Changeset 2361

Timestamp:

01/22/11 04:48:29 (1 year ago)

Author:

jmdavis

Message:

Various adjustments to the documentation in std.datetime and std.file.

This should fix the current ddoc build errors or Windows.

Files:

• trunk/docsrc/std.ddoc (modified) (1 diff)
• trunk/phobos/std/datetime.d (modified) (27 diffs)
• trunk/phobos/std/file.d (modified) (12 diffs)

trunk/docsrc/std.ddoc

@@ -166 +166 @@
-    $(LI <a href="std_ctype.html" title="Simple character classification">std.ctype</a>)
-    $(LI <a href="std_date.html" title="Date and time functions">std.date</a>)
+    $(LI <a href="std_datetime.html" title="Date and time functions">std.datetime</a>)
-    $(LI <a href="std_demangle.html" title="Demangle D names">std.demangle</a>)
-    $(LI <a href="std_encoding.html" title="Character and string encoding">std.encoding</a>)

trunk/phobos/std/datetime.d

@@ -6 +6 @@
-    This module provides:
-    $(UL
-
+
+
-        $(LI Types to represent durations of time.)
-        $(LI Types to represent intervals of time.)
-        $(LI Types to represent ranges over intervals of time.)
-SysTime
-StopWatch
+$(D_PARAM SysTime)
+$(D_PARAM StopWatch)
-        $(LI Benchmarking functions.)
-        $(LI Various helper functions.)
@@ -36 +37 @@
-    series of time points.
-
-Date
-DateTime
-SysTime
+$(D_PARAM Date)
+$(D_PARAM DateTime)
+$(D_PARAM SysTime)
-    and time from the OS and/or do care about time zones), and StopWatch (a
-
-
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
+
-
-    Examples:
@@ -69 +71 @@
-    Note:
-        core.time is publicly imported by std.datetime, so if you're using
-DateTimeException
+$(D_PARAM DateTimeException)
-        is an alias for core.time's TimeException, so you don't need to worry
-        about core.time functions and std.datetime functions throwing a different
-        type of exception (except in the rare case that they throw something other
-TimeException or DateTimeException
+$(D_PARAM TimeException) or $(D_PARAM DateTimeException)
-
-    See_Also:
-<a href="http://en.wikipedia.org/wiki/ISO_8601">ISO 8601</a>
-<a href="http://en.wikipedia.org/wiki/Tz_database">Wikipedia entry on TZ Database</a>
-<a href="http://en.wikipedia.org/wiki/List_of_tz_database_time_zones">List of Time Zones</a>
+$(WEB en.wikipedia.org/wiki/ISO_8601, ISO 8601)
+$(WEB en.wikipedia.org/wiki/Tz_database, Wikipedia entry on TZ Database)
+$(WEB en.wikipedia.org/wiki/List_of_tz_database_time_zones, List of Time Zones)
-
-    Copyright: Copyright 2010
-<a href="http://www.boost.org/LICENSE_1_0.txt">Boost License 1.0</a>
+$(WEB www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
-    Authors:   Jonathan M Davis and Kato Shoichi
-+/
@@ -306 +308 @@
-
-//==============================================================================
+// Section with other types.
+//==============================================================================
+
+/++
+    Exception type used by std.datetime.
+  +/
+alias TimeException DateTimeException;
+
+
+/++
+    Effectively a namespace to make it clear where its methods are getting
+    their time from. It cannot be instantiated.
+ +/
+final class Clock
+{
+public:
+
+    /++
+        Returns the current time in the local timezone.
+      +/
+    static SysTime currTime(immutable TimeZone tz = LocalTime())
+    {
+        return SysTime(currStdTime, tz);
+    }
+
+    unittest
+    {
+        version(enableWindowsTest)
+        {
+            assert(currTime(UTC()).timezone is UTC());
+
+            immutable unixTimeD = currTime().toUnixTime();
+            immutable unixTimeC = core.stdc.time.time(null);
+            immutable diff = unixTimeC - unixTimeD;
+
+            assertPred!">="(diff, -2);
+            assertPred!"<="(diff, 2);
+        }
+    }
+
+
+    /++
+        Returns the number of hnsecs since midnight, January 1st, 1 A.D. for the
+        current time.
+
+        Throws:
+            ErrnoException (on Posix) or Exception (on Windows) if it fails to
+            get the time of day.
+      +/
+    @trusted
+    static @property long currStdTime()
+    {
+        version(Windows)
+        {
+            //FILETIME represents hnsecs from midnight, January 1st, 1601.
+            enum hnsecsFrom1601 = 504_911_232_000_000_000L;
+
+            FILETIME fileTime;
+
+            GetSystemTimeAsFileTime(&fileTime);
+
+            ulong tempHNSecs = fileTime.dwHighDateTime;
+            tempHNSecs <<= 32;
+            tempHNSecs |= fileTime.dwLowDateTime;
+
+            return cast(long)tempHNSecs + hnsecsFrom1601;
+        }
+        else version(Posix)
+        {
+            enum hnsecsToUnixEpoch = 621_355_968_000_000_000L;
+
+            static if(is(typeof(clock_gettime)))
+            {
+                timespec ts;
+
+                if(clock_gettime(CLOCK_REALTIME, &ts) != 0)
+                    throw new TimeException("Failed in clock_gettime().");
+
+                return convert!("seconds", "hnsecs")(ts.tv_sec) +
+                       ts.tv_nsec / 100 +
+                       hnsecsToUnixEpoch;
+            }
+            else
+            {
+                timeval tv;
+
+                if(gettimeofday(&tv, null) != 0)
+                    throw new TimeException("Failed in gettimeofday().");
+
+                return convert!("seconds", "hnsecs")(tv.tv_sec) +
+                       convert!("usecs", "hnsecs")(tv.tv_usec) +
+                       hnsecsToUnixEpoch;
+            }
+        }
+    }
+
+
+    /++
+        The current system tick. The number of ticks per second varies from
+        system to system. This uses a monotonic clock, so it's intended for
+        precision timing by comparing relative time values, not for getting
+        the current system time.
+
+        Warning:
+            On some systems, the monotonic clock may stop counting when
+            the computer goes to sleep or hibernates. So, the monotonic
+            clock could be off if that occurs. This is known to happen
+            on Mac OS X. It has not been tested whether it occurs on
+            either Windows or on Linux.
+
+        Throws:
+            TimeException if it fails to get the time.
+      +/
+    @safe
+    static @property TickDuration currSystemTick()
+    {
+        return TickDuration.currSystemTick();
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto t = Clock.currSystemTick;
+            assert(t.length > 0);
+        }
+    }
+
+
+    /++
+        The current number of system ticks since the application started.
+        The number of ticks per second varies from system to system.
+        This uses a monotonic clock.
+
+        Warning:
+            On some systems, the monotonic clock may stop counting when
+            the computer goes to sleep or hibernates. So, the monotonic
+            clock could be off if that occurs. This is known to happen
+            on Mac OS X. It has not been tested whether it occurs on
+            either Windows or on Linux.
+
+        Throws:
+            ErrnoException (on Posix) or Exception (on Windows) if it fails to
+            get the time of day.
+      +/
+    @safe
+    static @property TickDuration currAppTick()
+    {
+        return currSystemTick - TickDuration.appOrigin;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto a = Clock.currSystemTick;
+            auto b = Clock.currAppTick;
+            assert(a.length);
+            assert(a != b);
+        }
+    }
+
+
+private:
+
+    @disable this() {}
+}
+
+
+//==============================================================================
-// Section with time points.
-//==============================================================================
+
+
+/++
+    SysTime is the type used when you want to get the current time from the system
+    or if you're doing anything that involves time zones. Unlike DateTime, time
+    zone is an integral part of SysTime (though if all you care about is local
+    time, you can pretty much ignore time zones, and it will work, since it
+    defaults to using the local time zone). It holds its internal time in std time
+    (hnsecs since midnight, January 1st, 1 A.D. UTC), so it interfaces well with the
+    system time. However, that means that, unlike DateTime, it is not optimized
+    for calendar operations, and getting individual units from it such as years
+    or days is going to involve conversions and be less efficient.
+
+    Basically, if you care about calendar operations and don't necessarily care
+    about time zones, then DateTime would be the type to use. However, if what
+    you care about is the system time, then SysTime is the type to use.
+
+    $(D Clock.currTime()) will return the current time as a SysTime. If you want
+    to convert a SysTime to a Date or DateTime, simply cast it. And if you ever
+    want to convert a Date or DateTime to a SysTime, use SysTime's constructor,
+    and you can pass in the intended time zone with it (or don't pass in a
+    TimeZone, and the local time zone will be used).
+
+    If you care about using time zones other than local time or UTC, you can use
+    PosixTimeZone on Posix systems (or on Windows, if you provide the TZ Database
+    files), and you can use WindowsTimeZone on Windows systems. The time in SysTime
+    is kept internally in hnsecs from midnight, January 1st, 1 A.D. UTC. So, you
+    never get conversion errors when changing the time zone of a SysTime (since,
+    if the hnecs were kept in local time, DST would cause problems with conversions).
+    LocalTime is the TimeZone class which represents the local time, and UTC is the
+    TimeZone class which represents UTC. SysTime uses LocalTime if no TimeZone is
+    provided. For more details on time zones, look at the documentation for
+    TimeZone, PosixTimeZone, and WindowsTimeZone.
+
+    SysTime's range is from approximately 29,000 B.C. to 29,000 A.D.
+  +/
+struct SysTime
+{
+public:
+
+    /++
+        Params:
+            dateTime = The DateTime to use to set this SysTime's internal std
+                       time. As DateTime has no concept of time zone, tz is used
+                       as its time zone.
+            tz       = The TimeZone to use for this SysTime. If null, LocalTime
+                       will be used. The given DateTime is assumed to be in the
+                       given time zone.
+      +/
+    this(in DateTime dateTime, immutable TimeZone tz = null) nothrow
+    {
+        try
+            this(dateTime, FracSec.from!"hnsecs"(0), tz);
+        catch(Exception e)
+            assert(0, "FracSec's constructor threw when it shouldn't have.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime.init, UTC())._stdTime, 0);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 30, 33), UTC())._stdTime, 450_330_000_000L);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 30, 33), UTC())._stdTime, -413_670_000_000L);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), UTC())._stdTime, 0);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 1), UTC())._stdTime, 10_000_000L);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), UTC())._stdTime, -10_000_000L);
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(-60)).stdTime, 36_000_000_000L);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(0)).stdTime, 0);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(60)).stdTime, -36_000_000_000L);
+        }
+    }
+
+
+    /++
+        Params:
+            dateTime = The DateTime to use to set this SysTime's internal std time.
+                       As DateTime has no concept of time zone, tz is used as its
+                       time zone.
+            fsec     = The fractional seconds portion of the time.
+            tz       = The TimeZone to use for this SysTime. If null, LocalTime will
+                       be used. The given DateTime is assumed to be in the given
+                       time zone.
+      +/
+    this(in DateTime dateTime, in FracSec fsec, immutable TimeZone tz = null) nothrow
+    {
+        if(tz is null)
+            _timezone = LocalTime();
+        else
+            _timezone = tz;
+
+        try
+        {
+            immutable dateDiff = (dateTime.date - Date(1, 1, 1)).total!"hnsecs";
+            immutable todDiff = (dateTime.timeOfDay - TimeOfDay(0, 0, 0)).total!"hnsecs";
+
+            immutable adjustedTime = dateDiff + todDiff + fsec.hnsecs;
+            immutable standardTime = _timezone.tzToUTC(adjustedTime);
+
+            this(standardTime, _timezone.get);
+        }
+        catch(Exception e)
+            assert(0, "Date, TimeOfDay, or DateTime's constructor threw when it shouldn't have.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime.init, FracSec.init, UTC())._stdTime, 0);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 30, 33), FracSec.init, UTC())._stdTime, 450_330_000_000L);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 30, 33), FracSec.init, UTC())._stdTime, -413_670_000_000L);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(1), UTC())._stdTime, 10_000L);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC())._stdTime, -10_000L);
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).stdTime, -1);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1), UTC()).stdTime, -9_999_999);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0), UTC()).stdTime, -10_000_000);
+        }
+    }
+
+
+    /++
+        Params:
+            date = The Date to use to set this SysTime's internal std time.
+                   As Date has no concept of time zone, tz is used as its
+                   time zone.
+            tz   = The TimeZone to use for this SysTime. If null, LocalTime will
+                   be used. The given Date is assumed to be in the given time zone.
+      +/
+    this(in Date date, immutable TimeZone tz = null) nothrow
+    {
+        if(tz is null)
+            _timezone = LocalTime();
+        else
+            _timezone = tz;
+
+        try
+        {
+            immutable adjustedTime = (date - Date(1, 1, 1)).total!"hnsecs";
+            immutable standardTime = _timezone.tzToUTC(adjustedTime);
+
+            this(standardTime, _timezone.get);
+        }
+        catch(Exception e)
+            assert(0, "Date's constructor through when it shouldn't have");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(Date.init, UTC())._stdTime, 0);
+            assertPred!"=="(SysTime(Date(1, 1, 1), UTC())._stdTime, 0);
+            assertPred!"=="(SysTime(Date(1, 1, 2), UTC())._stdTime, 864000000000);
+            assertPred!"=="(SysTime(Date(0, 12, 31), UTC())._stdTime, -864000000000);
+        }
+    }
+
+
+    /++
+        Note:
+            Whereas the other constructors take in the given date/time, assume
+            that it's in the given time zone, and convert it to hnsecs in UTC
+            since midnight, January 1st, 1 A.D. UTC - i.e. std time - this constructor
+            takes a std time, which is specifically already in UTC, so no conversion
+            takes place. Of course, the various getter properties and functions
+            will use the given time zone's conversion function to convert the
+            results to that time zone, but no conversion of the arguments to
+            this constructor takes place.
+
+        Params:
+            stdTime = The number of hnsecs since midnight, January 1st, 1 A.D. UTC.
+            tz    = The TimeZone to use for this SysTime. If null, LocalTime will be used.
+      +/
+    this(long stdTime, immutable TimeZone tz = null) pure nothrow
+    {
+        _stdTime = stdTime;
+
+        if(tz is null)
+            _timezone = LocalTime();
+        else
+            _timezone = tz;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0)._stdTime, 0);
+        }
+    }
+
+
+    /++
+        Params:
+            rhs = The SysTime to assign to this one.
+      +/
+    ref SysTime opAssign(const ref SysTime rhs) pure nothrow
+    {
+        _stdTime = rhs._stdTime;
+        _timezone = rhs._timezone.get;
+
+        return this;
+    }
+
+
+    /++
+        Params:
+            rhs = The SysTime to assign to this one.
+      +/
+    ref SysTime opAssign(SysTime rhs) pure nothrow
+    {
+        _stdTime = rhs._stdTime;
+        _timezone = rhs._timezone.get;
+
+        return this;
+    }
+
+
+    /++
+        Checks for equality between this SysTime and the given
+        SysTime.
+
+        Note that the time zone is ignored. Only the internal
+        std times (which are in UTC) are compared.
+     +/
+    bool opEquals(const ref SysTime rhs) const pure nothrow
+    {
+        return _stdTime == rhs._stdTime;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto a = SysTime(DateTime.init, UTC());
+            auto b = SysTime(0, UTC());
+            assert(a == b);
+            assertPred!"=="(a, b);
+            assertPred!"=="(SysTime(DateTime.init, UTC()), SysTime(0, UTC()));
+            assertPred!"=="(SysTime(Date.init, UTC()), SysTime(0, UTC()));
+            assertPred!"=="(SysTime(0), SysTime(0));
+
+            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
+            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
+            assertPred!"=="(SysTime(Date(1, 7, 1)), SysTime(Date(1, 7, 1)));
+            assertPred!"=="(SysTime(Date(1, 1, 6)), SysTime(Date(1, 1, 6)));
+
+            assertPred!"=="(SysTime(Date(1999, 7, 1)), SysTime(Date(1999, 7, 1)));
+            assertPred!"=="(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 6)));
+
+            assertPred!"=="(SysTime(Date(1, 7, 6)), SysTime(Date(1, 7, 6)));
+
+            assertPred!"=="(SysTime(DateTime(1999, 1, 1, 0, 0, 0)), SysTime(Date(1999, 1, 1)));
+            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 0, 0, 0)));
+
+            assertPred!"!="(SysTime(DateTime(1999, 1, 1, 11, 30, 20)), SysTime(Date(1999, 1, 1)));
+            assertPred!"!="(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 11, 30, 20)));
+
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))));
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))));
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))));
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
+
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))));
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))));
+            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
+                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
+
+            {
+                auto sysUTC = SysTime(Date(1999, 1, 1));
+                sysUTC.timezone = UTC();
+
+                auto sysLocal = SysTime(Date(1999, 1, 1));
+                sysUTC.timezone = LocalTime();
+
+                assertPred!"=="(sysUTC, sysLocal);
+                assertPred!"=="(sysLocal, sysUTC);
+
+                if(!localTimeIsUTC)
+                {
+                    assertPred!"!="(SysTime(Date(1999, 1, 1), UTC()), SysTime(Date(1999, 1, 1), LocalTime()));
+                    assertPred!"!="(SysTime(Date(1999, 7, 1), LocalTime()), SysTime(Date(1999, 7, 1), UTC()));
+                }
+            }
+
+            {
+                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
+                sysUTC.timezone = UTC();
+
+                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
+                sysSimple.timezone = new SimpleTimeZone(-360);
+
+                assertPred!"=="(sysUTC, sysSimple);
+                assertPred!"=="(sysSimple, sysUTC);
+
+                assertPred!"!="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()),
+                               SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone));
+                assertPred!"!="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone),
+                               SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()));
+            }
+
+            {
+                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC());
+                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), new SimpleTimeZone(240));
+
+                assertPred!"!="(sysUTC, sysSimple);
+                assertPred!"!="(sysSimple, sysUTC);
+
+                sysUTC = SysTime(DateTime(Date(1999, 7, 5), TimeOfDay(20, 0, 0)), UTC());
+
+                assertPred!"=="(sysUTC, sysSimple);
+                assertPred!"=="(sysSimple, sysUTC);
+            }
+
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            static assert(__traits(compiles, st == st));
+            static assert(__traits(compiles, st == cst));
+            //static assert(__traits(compiles, st == ist));
+            static assert(__traits(compiles, cst == st));
+            static assert(__traits(compiles, cst == cst));
+            //static assert(__traits(compiles, cst == ist));
+            //static assert(__traits(compiles, ist == st));
+            //static assert(__traits(compiles, ist == cst));
+            //static assert(__traits(compiles, ist == ist));
+        }
+    }
+
+
+    /++
+        Compares this SysTime with the given SysTime.
+
+        Time zone is irrelevant to comparing SysTimes.
+
+        Returns:
+            $(TABLE
+            $(TR $(TD this &lt; rhs) $(TD &lt; 0))
+            $(TR $(TD this == rhs) $(TD 0))
+            $(TR $(TD this &gt; rhs) $(TD &gt; 0))
+            )
+     +/
+    int opCmp(in SysTime rhs) const pure nothrow
+    {
+        if(_stdTime < rhs._stdTime)
+            return -1;
+        if(_stdTime > rhs._stdTime)
+            return 1;
+
+        return 0;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!("opCmp", "==")(SysTime(DateTime.init, UTC()), SysTime(0));
+            assertPred!("opCmp", "==")(SysTime(Date.init, UTC()), SysTime(0));
+
+            assertPred!("opCmp", "==")(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
+            assertPred!("opCmp", "==")(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
+            assertPred!("opCmp", "==")(SysTime(Date(1, 7, 1)), SysTime(Date(1, 7, 1)));
+            assertPred!("opCmp", "==")(SysTime(Date(1, 1, 6)), SysTime(Date(1, 1, 6)));
+
+            assertPred!("opCmp", "==")(SysTime(Date(1999, 7, 1)), SysTime(Date(1999, 7, 1)));
+            assertPred!("opCmp", "==")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 6)));
+
+            assertPred!("opCmp", "==")(SysTime(Date(1, 7, 6)), SysTime(Date(1, 7, 6)));
+
+            assertPred!("opCmp", ">")(SysTime(DateTime(1999, 1, 1, 11, 30, 20)), SysTime(Date(1999, 1, 1)));
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 11, 30, 20)));
+
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(2000, 7, 6)));
+            assertPred!("opCmp", ">")(SysTime(Date(2000, 7, 6)), SysTime(Date(1999, 7, 6)));
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 8, 6)));
+            assertPred!("opCmp", ">")(SysTime(Date(1999, 8, 6)), SysTime(Date(1999, 7, 6)));
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 7)));
+            assertPred!("opCmp", ">")(SysTime(Date(1999, 7, 7)), SysTime(Date(1999, 7, 6)));
+
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 8, 7)), SysTime(Date(2000, 7, 6)));
+            assertPred!("opCmp", ">")(SysTime(Date(2000, 8, 6)), SysTime(Date(1999, 7, 7)));
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 7)), SysTime(Date(2000, 7, 6)));
+            assertPred!("opCmp", ">")(SysTime(Date(2000, 7, 6)), SysTime(Date(1999, 7, 7)));
+            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 7)), SysTime(Date(1999, 8, 6)));
+            assertPred!("opCmp", ">")(SysTime(Date(1999, 8, 6)), SysTime(Date(1999, 7, 7)));
+
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0)))),
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
+
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
+                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                     SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 31, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
+                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
+
+            //Test B.C.
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33))),
+                                       SysTime(DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
+
+            //Test Both
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))));
+
+            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(1999, 6, 6), TimeOfDay(12, 30, 33))));
+            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 6, 8), TimeOfDay(12, 30, 33))),
+                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
+
+            {
+                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
+                sysUTC.timezone = UTC();
+
+                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
+                sysSimple.timezone = new SimpleTimeZone(-360);
+
+                assertPred!("opCmp", "==")(sysUTC, sysSimple);
+                assertPred!("opCmp", "==")(sysSimple, sysUTC);
+
+                assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()),
+                                         SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone));
+                assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone),
+                                         SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()));
+            }
+
+            {
+                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC());
+                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), new SimpleTimeZone(240));
+
+                assertPred!("opCmp", ">")(sysUTC, sysSimple);
+                assertPred!("opCmp", "<")(sysSimple, sysUTC);
+
+                sysUTC = SysTime(DateTime(Date(1999, 7, 5), TimeOfDay(20, 0, 0)), UTC());
+
+                assertPred!("opCmp", "==")(sysUTC, sysSimple);
+                assertPred!("opCmp", "==")(sysSimple, sysUTC);
+            }
+
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
+            static assert(__traits(compiles, st.opCmp(st)));
+            static assert(__traits(compiles, st.opCmp(cst)));
+            //static assert(__traits(compiles, st.opCmp(ist)));
+            static assert(__traits(compiles, cst.opCmp(st)));
+            static assert(__traits(compiles, cst.opCmp(cst)));
+            //static assert(__traits(compiles, cst.opCmp(ist)));
+            //static assert(__traits(compiles, ist.opCmp(st)));
+            //static assert(__traits(compiles, ist.opCmp(cst)));
+            //static assert(__traits(compiles, ist.opCmp(ist)));
+        }
+    }
+
+
+    /++
+        Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
+        are B.C.
+     +/
+    @property short year() const nothrow
+    {
+        return (cast(Date)this).year;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).year, 1);
+            assertPred!"=="(SysTime(1, UTC()).year, 1);
+            assertPred!"=="(SysTime(-1, UTC()).year, 0);
+            assertPred!"=="(SysTime(DateTime(12, 1, 1, 0, 0, 0)).year, 12);
+            assertPred!"=="(SysTime(DateTime(-12, 1, 1, 0, 0, 0)).year, -12);
+            assertPred!"=="(SysTime(Date(1999, 7, 6)).year, 1999);
+            assertPred!"=="(SysTime(Date(-1999, 7, 6)).year, -1999);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.year));
+            //static assert(__traits(compiles, ist.year));
+        }
+    }
+
+
+    /++
+        Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
+        are B.C.
+
+        Params:
+            year = The year to set this SysTime's year to.
+
+        Throws:
+            DateTimeException if the new year is not a leap year and the resulting
+            date would be on February 29th.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).year == 1999);
+assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).year == 2010);
+assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).year == -7);
+--------------------
+     +/
+    @property void year(int year)
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.year = year;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testST(SysTime st, int year, in SysTime expected, size_t line = __LINE__)
+            {
+                st.year = year;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1999, SysTime(Date(1999, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 0, SysTime(Date(0, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), -1999, SysTime(Date(-1999, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), -1999, SysTime(DateTime(-1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 1999, SysTime(Date(1999, 1, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 0, SysTime(Date(0, 1, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), -1999, SysTime(Date(-1999, 1, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), -1999, SysTime(DateTime(-1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(12, 7, 2)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(5, 7, 2)));
+            testST(SysTime(Date(0, 7, 2)), 999, SysTime(Date(999, 7, 2)));
+            testST(SysTime(Date(-1202, 7, 2)), 2300, SysTime(Date(2300, 7, 2)));
+
+            testST(SysTime(Date(1, 7, 2)), -12, SysTime(Date(-12, 7, 2)));
+            testST(SysTime(Date(5007, 7, 2)), -5, SysTime(Date(-5, 7, 2)));
+            testST(SysTime(Date(0, 7, 2)), -999, SysTime(Date(-999, 7, 2)));
+            testST(SysTime(Date(-1202, 7, 2)), -2300, SysTime(Date(-2300, 7, 2)));
+
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -1, SysTime(DateTime(-1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(999, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(2010, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -507, SysTime(DateTime(-507, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(2300, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -1, SysTime(DateTime(-1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(999, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(2010, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -507, SysTime(DateTime(-507, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(2300, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(12, 1, 1, 0, 0, 0), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.year = 7));
+            //static assert(!__traits(compiles, ist.year = 7));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).year == 1999);
+            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).year == 2010);
+            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).year == -7);
+        }
+    }
+
+
+    /++
+        Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
+
+        Throws:
+            DateTimeException if $(D isAD) is true.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(0, 1, 1, 12, 30, 33)).yearBC == 1);
+assert(SysTime(DateTime(-1, 1, 1, 10, 7, 2)).yearBC == 2);
+assert(SysTime(DateTime(-100, 1, 1, 4, 59, 0)).yearBC == 101);
+--------------------
+     +/
+    @property ushort yearBC() const
+    {
+        return (cast(Date)this).yearBC;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(Date(1, 1, 1), UTC())));
+            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(0, UTC())));
+            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(1, UTC())));
+
+            assertPred!"=="(SysTime(-1, UTC()).yearBC, 1);
+            assertPred!"=="(SysTime(DateTime(-12, 1, 1, 0, 0, 0)).yearBC, 13);
+
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.year = 12));
+            static assert(!__traits(compiles, cst.year = 12));
+            //static assert(!__traits(compiles, ist.year = 12));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(0, 1, 1, 12, 30, 33)).yearBC == 1);
+            assert(SysTime(DateTime(-1, 1, 1, 10, 7, 2)).yearBC == 2);
+            assert(SysTime(DateTime(-100, 1, 1, 4, 59, 0)).yearBC == 101);
+        }
+    }
+
+
+    /++
+        Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
+
+        Params:
+            year = The year B.C. to set this SysTime's year to.
+
+        Throws:
+            DateTimeException if a non-positive value is given.
+
+        Examples:
+--------------------
+auto st = SysTime(DateTime(2010, 1, 1, 7, 30, 0));
+st.yearBC = 1;
+assert(st == SysTime(DateTime(0, 1, 1, 7, 30, 0)));
+
+st.yearBC = 10;
+assert(st == SysTime(DateTime(-9, 1, 1, 7, 30, 0)));
+--------------------
+     +/
+    @property void yearBC(int year)
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.yearBC = year;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, int year)
+            {
+                st.yearBC = year;
+            }
+
+            static void testST(SysTime st, int year, in SysTime expected, size_t line = __LINE__)
+            {
+                st.yearBC = year;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 0));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), -1));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), -1202));
+
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1999, SysTime(Date(-1998, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1, SysTime(Date(0, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(-1998, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(-11, 7, 2)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(-4, 7, 2)));
+            testST(SysTime(Date(0, 7, 2)), 999, SysTime(Date(-998, 7, 2)));
+            testST(SysTime(Date(-1202, 7, 2)), 2300, SysTime(Date(-2299, 7, 2)));
+
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(-998, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(-2009, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(-2299, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(-5006, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(-998, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(-2009, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(-2299, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(-5006, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(-11, 1, 1, 0, 0, 0), UTC()));
+
+            {
+                auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+                const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+                //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+                static assert(__traits(compiles, st.yearBC = 12));
+                static assert(!__traits(compiles, cst.yearBC = 12));
+                //static assert(!__traits(compiles, ist.yearBC = 12));
+            }
+
+            //Verify Examples.
+            {
+                auto st = SysTime(DateTime(2010, 1, 1, 7, 30, 0));
+                st.yearBC = 1;
+                assert(st == SysTime(DateTime(0, 1, 1, 7, 30, 0)));
+
+                st.yearBC = 10;
+                assert(st == SysTime(DateTime(-9, 1, 1, 7, 30, 0)));
+            }
+        }
+    }
+
+
+    /++
+        Month of a Gregorian Year.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).month == 7);
+assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).month == 10);
+assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).month == 4);
+--------------------
+     +/
+    @property Month month() const nothrow
+    {
+        return (cast(Date)this).month;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).month, 1);
+            assertPred!"=="(SysTime(1, UTC()).month, 1);
+            assertPred!"=="(SysTime(-1, UTC()).month, 12);
+            assertPred!"=="(SysTime(DateTime(1, 12, 1, 0, 0, 0)).month, 12);
+            assertPred!"=="(SysTime(DateTime(0, 12, 1, 0, 0, 0)).month, 12);
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)).month, 7);
+            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 12, 30, 33)).month, 7);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.month));
+            //static assert(__traits(compiles, ist.month));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).month == 7);
+            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).month == 10);
+            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).month == 4);
+        }
+    }
+
+
+    /++
+        Month of a Gregorian Year.
+
+        Params:
+            month = The month to set this SysTime's month to.
+
+        Throws:
+            DateTimeException if the given month is not a valid month.
+     +/
+    @property void month(Month month)
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.month = month;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, Month month)
+            {
+                st.month = month;
+            }
+
+            static void testST(SysTime st, Month month, in SysTime expected, size_t line = __LINE__)
+            {
+                st.month = month;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 1, 12, 30, 33)), cast(Month)0));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 1, 12, 30, 33)), cast(Month)13));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 29, 12, 30, 33)), cast(Month)2));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 7, 31, 12, 30, 33)), cast(Month)6));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(4, 7, 30, 12, 30, 33)), cast(Month)2));
+
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)1, SysTime(Date(1, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)7, SysTime(Date(1, 7, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)12, SysTime(Date(1, 12, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)7, SysTime(DateTime(1, 7, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)1, SysTime(Date(0, 1, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)7, SysTime(Date(0, 7, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)12, SysTime(Date(0, 12, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)7, SysTime(DateTime(0, 7, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), cast(Month)12, SysTime(Date(1, 12, 2)));
+            testST(SysTime(Date(5007, 7, 2)), cast(Month)5, SysTime(Date(5007, 5, 2)));
+            testST(SysTime(Date(0, 7, 2)), cast(Month)7, SysTime(Date(0, 7, 2)));
+            testST(SysTime(Date(-1202, 7, 2)), cast(Month)1, SysTime(Date(-1202, 1, 2)));
+
+            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)), cast(Month)7, SysTime(DateTime(1, 7, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)));
+            testST(SysTime(DateTime(1, 11, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)), cast(Month)1, SysTime(DateTime(1, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)));
+            testST(SysTime(DateTime(1, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)), cast(Month)2, SysTime(DateTime(1, 2, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)));
+            testST(SysTime(DateTime(1, 7, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)),cast(Month) 6, SysTime(DateTime(1, 6, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)));
+            testST(SysTime(DateTime(4, 7, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)2, SysTime(DateTime(4, 2, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(4, 7, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)8, SysTime(DateTime(4, 8, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)));
+
+            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)), cast(Month)12, SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)));
+            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)), cast(Month)7, SysTime(DateTime(1207, 7, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)));
+            testST(SysTime(DateTime(1207, 11, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)), cast(Month)1, SysTime(DateTime(1207, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(1207, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)), cast(Month)2, SysTime(DateTime(1207, 2, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)));
+            testST(SysTime(DateTime(1207, 7, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)), cast(Month)6, SysTime(DateTime(1207, 6, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)));
+
+            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)), cast(Month)7, SysTime(DateTime(0, 7, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)));
+            testST(SysTime(DateTime(0, 11, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)), cast(Month)1, SysTime(DateTime(0, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)));
+            testST(SysTime(DateTime(0, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)), cast(Month)2, SysTime(DateTime(0, 2, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)));
+            testST(SysTime(DateTime(0, 7, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)), cast(Month)6, SysTime(DateTime(0, 6, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)));
+
+            testST(SysTime(DateTime(0, 12, 30, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)11, SysTime(DateTime(0, 11, 30, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(-1, 7, 28, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)2, SysTime(DateTime(-1, 2, 28, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 7, 29, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)2, SysTime(DateTime(0, 2, 29, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 7, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)2, SysTime(DateTime(0, 2, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(0, 7, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)8, SysTime(DateTime(0, 8, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)));
+
+            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)), cast(Month)12, SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)));
+            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)), cast(Month)7, SysTime(DateTime(-9999, 7, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)));
+            testST(SysTime(DateTime(-9999, 11, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)), cast(Month)1, SysTime(DateTime(-9999, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(-9999, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)), cast(Month)2, SysTime(DateTime(-9999, 2, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)));
+            testST(SysTime(DateTime(-9999, 7, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)), cast(Month)6, SysTime(DateTime(-9999, 6, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)));
+
+            testST(SysTime(0, UTC()), cast(Month)12, SysTime(DateTime(1, 12, 1, 0, 0, 0), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.month = 12));
+            //static assert(!__traits(compiles, ist.month = 12));
+        }
+    }
+
+
+    /++
+        Day of a Gregorian Month.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).day == 6);
+assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).day == 4);
+assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).day == 5);
+--------------------
+     +/
+    @property ubyte day() const nothrow
+    {
+        return (cast(Date)this).day;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).day, 1);
+            assertPred!"=="(SysTime(1, UTC()).day, 1);
+            assertPred!"=="(SysTime(-1, UTC()).day, 31);
+            assertPred!"=="(SysTime(DateTime(50, 2, 4)).day, 4);
+            assertPred!"=="(SysTime(DateTime(50, 2, 4, 0, 0, 1)).day, 4);
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6)).day, 6);
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 0, 0, 0)).day, 6);
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)).day, 6);
+            assertPred!"=="(SysTime(DateTime(-50, 2, 4)).day, 4);
+            assertPred!"=="(SysTime(DateTime(-50, 2, 4, 0, 0, 1)).day, 4);
+            assertPred!"=="(SysTime(Date(-1999, 7, 6)).day, 6);
+            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 0, 0, 0)).day, 6);
+            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 12, 30, 33)).day, 6);
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 12, 0, 0, 0)).day, 12);
+            assertPred!"=="(SysTime(DateTime(0, 1, 12, 0, 0, 0)).day, 12);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.day));
+            //static assert(__traits(compiles, ist.day));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).day == 6);
+            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).day == 4);
+            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).day == 5);
+        }
+    }
+
+
+    /++
+        Day of a Gregorian Month.
+
+        Params:
+            day = The day of the month to set this SysTime's day to.
+
+        Throws:
+            DateTimeException if the given day is not a valid day of the current
+            month.
+     +/
+    @property void day(int day)
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.day = day;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, int day)
+            {
+                st.day = day;
+            }
+
+            static void testST(SysTime st, int day, in SysTime expected, size_t line = __LINE__)
+            {
+                st.day = day;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 0));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 2, 1)), 29));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(4, 2, 1)), 30));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 3, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 4, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 5, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 6, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 7, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 8, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 9, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 10, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 11, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 12, 1)), 32));
+
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 2, 1)), 28));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(4, 2, 1)), 29));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 3, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 4, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 5, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 6, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 7, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 8, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 9, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 10, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 11, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 12, 1)), 31));
+
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1, SysTime(Date(1, 1, 1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 7, SysTime(Date(1, 1, 7)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 12, SysTime(Date(1, 1, 12)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 7, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 12, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(1, 7, 12)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(5007, 7, 5)));
+
+            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 29, SysTime(DateTime(1, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 29, SysTime(DateTime(999, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(900_000)));
+
+            //Test B.C.
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 0));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 2, 1)), 29));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(0, 2, 1)), 30));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 3, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 4, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 5, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 6, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 7, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 8, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 9, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 10, 1)), 32));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 11, 1)), 31));
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 12, 1)), 32));
+
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 2, 1)), 28));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(0, 2, 1)), 29));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 3, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 4, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 5, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 6, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 7, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 8, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 9, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 10, 1)), 31));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 11, 1)), 30));
+            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 12, 1)), 31));
+
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 1, SysTime(Date(0, 1, 1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 7, SysTime(Date(0, 1, 7)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 12, SysTime(Date(0, 1, 12)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 7, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 12, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(0, 7, 2)), 7, SysTime(Date(0, 7, 7)));
+            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(Date(-1202, 7, 1)));
+
+            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 29, SysTime(DateTime(0, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 29, SysTime(DateTime(-1, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(900_000)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 12, 0, 0, 0), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.day = 27));
+            //static assert(!__traits(compiles, ist.day = 27));
+        }
+    }
+
+
+    /++
+        Hours past midnight.
+     +/
+    @property ubyte hour() const nothrow
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        return cast(ubyte)getUnitsFromHNSecs!"hours"(hnsecs);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).hour, 0);
+            assertPred!"=="(SysTime(1, UTC()).hour, 0);
+            assertPred!"=="(SysTime(-1, UTC()).hour, 23);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 0, 0)).hour, 12);
+            assertPred!"=="(SysTime(DateTime(0, 1, 1, 12, 0, 0)).hour, 12);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.hour));
+            //static assert(__traits(compiles, ist.hour));
+        }
+    }
+
+
+    /++
+        Hours past midnight.
+
+        Params:
+            hour = The hours to set this SysTime's hour to.
+
+        Throws:
+            DateTimeException if the given hour are not a valid hour of the day.
+     +/
+    @property void hour(int hour)
+    {
+        enforceValid!"hours"(hour);
+
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
+        immutable daysHNSecs = convert!("days", "hnsecs")(days);
+        immutable negative = hnsecs < 0;
+
+        if(negative)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
+        hnsecs += convert!("hours", "hnsecs")(hour);
+
+        if(negative)
+            hnsecs -= convert!("hours", "hnsecs")(24);
+
+        adjTime = daysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, int hour)
+            {
+                st.hour = hour;
+            }
+
+            static void testST(SysTime st, int hour, in SysTime expected, size_t line = __LINE__)
+            {
+                st.hour = hour;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 24));
+
+            //Test A.D.
+            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 1, 0, 0)));
+            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 7, 0, 0)));
+            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 1, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 7, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 1, 59, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 7, 59, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 12, 59, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 1, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 7, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 12, 59, 59), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 12, 0, 0)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 5, 0, 0)));
+
+            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(900_000)));
+
+            //Test B.C.
+            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 1, 0, 0)));
+            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 7, 0, 0)));
+            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 12, 0, 0)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 1, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 7, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 12, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 1, 59, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 7, 59, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 12, 59, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 1, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 7, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 12, 59, 59), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 7, 0, 0)));
+            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 1, 0, 0)));
+
+            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(900_000)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.hour = 27));
+            //static assert(!__traits(compiles, ist.hour = 27));
+        }
+    }
+
+
+    /++
+        Minutes past the current hour.
+     +/
+    @property ubyte minute() const nothrow
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
+
+        return cast(ubyte)getUnitsFromHNSecs!"minutes"(hnsecs);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).minute, 0);
+            assertPred!"=="(SysTime(1, UTC()).minute, 0);
+            assertPred!"=="(SysTime(-1, UTC()).minute, 59);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 30, 0)).minute, 30);
+            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 30, 0)).minute, 30);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.minute));
+            //static assert(__traits(compiles, ist.minute));
+        }
+    }
+
+
+    /++
+        Minutes past the current hour.
+
+        Params:
+            minutes = The minute to set this SysTime's minute to.
+
+        Throws:
+            DateTimeException if the given minute are not a valid minute of an
+            hour.
+     +/
+    @property void minute(int minute)
+    {
+        enforceValid!"minutes"(minute);
+
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
+        immutable daysHNSecs = convert!("days", "hnsecs")(days);
+        immutable negative = hnsecs < 0;
+
+        if(negative)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+        hnsecs = removeUnitsFromHNSecs!"minutes"(hnsecs);
+
+        hnsecs += convert!("hours", "hnsecs")(hour);
+        hnsecs += convert!("minutes", "hnsecs")(minute);
+
+        if(negative)
+            hnsecs -= convert!("hours", "hnsecs")(24);
+
+        adjTime = daysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, int minute)
+            {
+                st.minute = minute;
+            }
+
+            static void testST(SysTime st, int minute, in SysTime expected, size_t line = __LINE__)
+            {
+                st.minute = minute;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 60));
+
+            //Test A.D.
+            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 1, 0)));
+            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 7, 0)));
+            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 1, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 7, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 1, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 7, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 12, 59)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 1, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 7, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 12, 59), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 12, 0)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 5, 0)));
+
+            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(900_000)));
+
+            //Test B.C.
+            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 1, 0)));
+            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 7, 0)));
+            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 12, 0)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 1, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 7, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 12, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 1, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 7, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 12, 59)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 1, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 7, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 12, 59), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 7, 0)));
+            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 1, 0)));
+
+            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(900_000)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.minute = 27));
+            //static assert(!__traits(compiles, ist.minute = 27));
+        }
+    }
+
+
+    /++
+        Seconds past the current minute.
+     +/
+    @property ubyte second() const nothrow
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
+        hnsecs = removeUnitsFromHNSecs!"minutes"(hnsecs);
+
+        return cast(ubyte)getUnitsFromHNSecs!"seconds"(hnsecs);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).second, 0);
+            assertPred!"=="(SysTime(1, UTC()).second, 0);
+            assertPred!"=="(SysTime(-1, UTC()).second, 59);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33)).second, 33);
+            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 0, 33)).second, 33);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.second));
+            //static assert(__traits(compiles, ist.second));
+        }
+    }
+
+
+    /++
+        Seconds past the current minute.
+
+        Params
+            second = The second to set this SysTime's second to.
+
+        Throws:
+            DateTimeException if the given second are not a valid second of a minute.
+     +/
+    @property void second(int second)
+    {
+        enforceValid!"seconds"(second);
+
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
+        immutable daysHNSecs = convert!("days", "hnsecs")(days);
+        immutable negative = hnsecs < 0;
+
+        if(negative)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+        immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+        hnsecs = removeUnitsFromHNSecs!"seconds"(hnsecs);
+
+        hnsecs += convert!("hours", "hnsecs")(hour);
+        hnsecs += convert!("minutes", "hnsecs")(minute);
+        hnsecs += convert!("seconds", "hnsecs")(second);
+
+        if(negative)
+            hnsecs -= convert!("hours", "hnsecs")(24);
+
+        adjTime = daysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testSTInvalid(SysTime st, int second)
+            {
+                st.second = second;
+            }
+
+            static void testST(SysTime st, int second, in SysTime expected, size_t line = __LINE__)
+            {
+                st.second = second;
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 60));
+
+            //Test A.D.
+            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 1)));
+            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 7)));
+            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 7), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 7)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 12)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 1), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 7), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 12), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 0, 12)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 0, 5)));
+
+            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(900_000)));
+
+            //Test B.C.
+            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 1)));
+            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 7)));
+            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 12)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 7), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 12), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 7)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 12)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 1), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 7), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 12), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 0, 7)));
+            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 0, 1)));
+
+            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(70)));
+            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(700)));
+            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(7000)));
+            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(70_000)));
+            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(700_000)));
+
+            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(9)));
+            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(90)));
+            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(900)));
+            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(9000)));
+            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(90_000)));
+            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(900_000)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.seconds = 27));
+            //static assert(!__traits(compiles, ist.seconds = 27));
+        }
+    }
+
+
+    /++
+        Fractional seconds passed the second.
+     +/
+    @property FracSec fracSec() const nothrow
+    {
+        try
+        {
+            auto hnsecs = removeUnitsFromHNSecs!"days"(adjTime);
+
+            if(hnsecs < 0)
+                hnsecs += convert!("hours", "hnsecs")(24);
+
+            hnsecs = removeUnitsFromHNSecs!"seconds"(hnsecs);
+
+            return FracSec.from!"hnsecs"(cast(int)hnsecs);
+        }
+        catch(Exception e)
+            assert(0, "FracSec.from!\"hnsecs\"() threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0, UTC()).fracSec.hnsecs, 0);
+            assertPred!"=="(SysTime(1, UTC()).fracSec.hnsecs, 1);
+            assertPred!"=="(SysTime(-1, UTC()).fracSec.hnsecs, 9_999_999);
+
+            assertPred!"=="(SysTime(DateTime(200, 3, 30, 1, 27, 19), FracSec.from!"hnsecs"(348), UTC()).fracSec.hnsecs, 348);
+            assertPred!"=="(SysTime(DateTime(-1, 2, 17, 4, 5, 22), FracSec.from!"hnsecs"(347), UTC()).fracSec.hnsecs, 347);
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502)).fracSec, FracSec.from!"hnsecs"(502));
+            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502)).fracSec, FracSec.from!"hnsecs"(502));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.fracSec));
+            //static assert(__traits(compiles, ist.fracSec));
+        }
+    }
+
+
+    /++
+        Fractional seconds passed the second.
+
+        Params
+            fracSec = The fractional seconds to set this SysTimes's fractional
+                      seconds to.
+     +/
+    @property void fracSec(FracSec fracSec) nothrow
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
+        immutable daysHNSecs = convert!("days", "hnsecs")(days);
+        immutable negative = hnsecs < 0;
+
+        if(negative)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+        immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+        immutable second = getUnitsFromHNSecs!"seconds"(hnsecs);
+
+        hnsecs = fracSec.hnsecs;
+        hnsecs += convert!("hours", "hnsecs")(hour);
+        hnsecs += convert!("minutes", "hnsecs")(minute);
+        hnsecs += convert!("seconds", "hnsecs")(second);
+
+        if(negative)
+            hnsecs -= convert!("hours", "hnsecs")(24);
+
+        adjTime = daysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void testST(SysTime st, int hnsecs, in SysTime expected, size_t line = __LINE__)
+            {
+                st.fracSec = FracSec.from!"hnsecs"(hnsecs);
+                assertPred!"=="(st, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            testST(SysTime(Date(1, 1, 1)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
+
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 0, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
+
+            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(12)));
+            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(5)));
+
+            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
+            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
+
+            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
+            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
+
+            //Test B.C.
+            testST(SysTime(Date(0, 1, 1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
+
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
+
+            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(7)));
+            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+
+            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
+            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
+
+            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
+            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
+            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
+
+            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12), UTC()));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.fracSec = FracSec.from!"msecs"(7)));
+            //static assert(!__traits(compiles, ist.fracSec = FracSec.from!"msecs"(7)));
+        }
+    }
+
+
+    /++
+        The total hnsecs from midnight, January 1st, 1 A.D. UTC. This is the internal
+        representation of SysTime.
+     +/
+    @property long stdTime() const pure nothrow
+    {
+        return _stdTime;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(0).stdTime, 0);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502), UTC()).stdTime, 330000502L);
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), UTC()).stdTime, 621355968000000000L);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.stdTime));
+            //static assert(__traits(compiles, ist.stdTime));
+        }
+    }
+
+
+    /++
+        The total hnsecs from midnight, January 1st, 1 A.D. UTC. This is the internal
+        representation of SysTime.
+
+        Params
+            stdTime = The number of hnsecs since January 1st, 1 A.D. UTC.
+     +/
+    @property void stdTime(long stdTime) pure nothrow
+    {
+        _stdTime = stdTime;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            {
+                auto st = SysTime(0, UTC());
+                st.stdTime = 330000502L;
+                assertPred!"=="(st, SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502), UTC()));
+            }
+
+            {
+                auto st = SysTime(0, UTC());
+                st.stdTime = 621355968000000000L;
+                assertPred!"=="(st, SysTime(DateTime(1970, 1, 1, 0, 0, 0), UTC()));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.stdTime = 27));
+            //static assert(!__traits(compiles, ist.stdTime = 27));
+        }
+    }
+
+
+    /++
+        The current time zone of this SysTime. Its internal time is always kept
+        in UTC, so there are no conversion issues between time zones due to DST.
+        Functions which return all or part of the time - such as hours - adjust
+        the time to this SysTime's time zone before returning.
+      +/
+    @property immutable(TimeZone) timezone() const pure nothrow
+    {
+        return _timezone.get;
+    }
+
+
+    /++
+        The current time zone of this SysTime. It's internal time is always kept
+        in UTC, so there are no conversion issues between time zones due to DST.
+        Functions which return all or part of the time - such as hours - adjust
+        the time to this SysTime's time zone before returning.
+      +/
+    @property void timezone(immutable TimeZone timezone) pure nothrow
+    {
+        _timezone = timezone;
+    }
+
+
+    /++
+        Returns whether DST is in effect for this SysTime.
+      +/
+    @property bool dstInEffect() const nothrow
+    {
+        return _timezone.dstInEffect(_stdTime);
+        //This function's unit testing is done in the time zone classes.
+    }
+
+
+    /++
+        Returns a SysTime with the same std time as this one, but with LocalTime
+        as its time zone.
+      +/
+    SysTime toLocalTime() const nothrow
+    {
+        return SysTime(_stdTime, LocalTime());
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            {
+                auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
+                assertPred!"=="(sysTime, sysTime.toLocalTime());
+                assertPred!"=="(sysTime._stdTime, sysTime.toLocalTime()._stdTime);
+                assert(sysTime.toLocalTime().timezone is LocalTime());
+                assert(sysTime.toLocalTime().timezone is sysTime.timezone);
+                assert(sysTime.toLocalTime().timezone !is UTC());
+            }
+
+            {
+                immutable stz = new SimpleTimeZone(-3 * 60);
+                auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27), stz);
+                assertPred!"=="(sysTime, sysTime.toLocalTime());
+                assertPred!"=="(sysTime._stdTime, sysTime.toLocalTime()._stdTime);
+                assert(sysTime.toLocalTime().timezone is LocalTime());
+                assert(sysTime.toLocalTime().timezone !is UTC());
+                assert(sysTime.toLocalTime().timezone !is stz);
+            }
+        }
+    }
+
+
+    /++
+        Returns a SysTime with the same std time as this one, but with UTC as
+        its time zone.
+      +/
+    SysTime toUTC() const pure nothrow
+    {
+        return SysTime(_stdTime, UTC());
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
+            assertPred!"=="(sysTime, sysTime.toUTC());
+            assertPred!"=="(sysTime._stdTime, sysTime.toUTC()._stdTime);
+            assert(sysTime.toUTC().timezone is UTC());
+            assert(sysTime.toUTC().timezone !is LocalTime());
+            assert(sysTime.toUTC().timezone !is sysTime.timezone);
+        }
+    }
+
+
+    /++
+        Returns a SysTime with the same std time as this one, but with given
+        time zone as its time zone.
+      +/
+    SysTime toOtherTZ(immutable TimeZone tz) const pure nothrow
+    {
+        return SysTime(_stdTime, tz);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            immutable stz = new SimpleTimeZone(11 * 60);
+            auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
+            assertPred!"=="(sysTime, sysTime.toOtherTZ(stz));
+            assertPred!"=="(sysTime._stdTime, sysTime.toOtherTZ(stz)._stdTime);
+            assert(sysTime.toOtherTZ(stz).timezone is stz);
+            assert(sysTime.toOtherTZ(stz).timezone !is LocalTime());
+            assert(sysTime.toOtherTZ(stz).timezone !is UTC());
+        }
+    }
+
+
+    /++
+        Returns a time_t which represents this SysTime.
+
+        If time_t is 32 bits, rather than 64, and the result can't fit in a 32-bit
+        value, then the closest value that can be held in 32 bits will be used
+        (so time_t.max if it goes over or time_t.min if it goes under).
+      +/
+    time_t toUnixTime() const pure nothrow
+    {
+        return stdTimeToUnixTime(_stdTime);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"usecs"(1), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"msecs"(1), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 1), UTC()).toUnixTime, 1);
+            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999_999), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC()).toUnixTime, 0);
+            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), UTC()).toUnixTime, -1);
+        }
+    }
+
+
+    /++
+        Returns a timeval which represents this SysTime.
+
+        If time_t is 32 bits, rather than 64, and the result can't fit in a 32-bit
+        value, then the closest value that can be held in 32 bits will be used
+        for tv_sec. (so time_t.max if it goes over or time_t.min if it goes under).
+      +/
+    timeval toTimeVal() const pure nothrow
+    {
+        immutable tv_sec = toUnixTime();
+
+        immutable fracHNSecs = removeUnitsFromHNSecs!"seconds"(_stdTime - 621355968000000000L);
+        immutable tv_usec = cast(int)convert!("hnsecs", "usecs")(fracHNSecs);
+
+        return timeval(tv_sec, tv_usec);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assert(SysTime(DateTime(1970, 1, 1), UTC()).toTimeVal() == timeval(0, 0));
+            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"hnsecs"(9), UTC()).toTimeVal() == timeval(0, 0));
+            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"hnsecs"(10), UTC()).toTimeVal() == timeval(0, 1));
+            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"usecs"(7), UTC()).toTimeVal() == timeval(0, 7));
+
+            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), UTC()).toTimeVal() == timeval(1, 0));
+            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(9), UTC()).toTimeVal() == timeval(1, 0));
+            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(10), UTC()).toTimeVal() == timeval(1, 1));
+            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"usecs"(7), UTC()).toTimeVal() == timeval(1, 7));
+
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toTimeVal() ==
+                   timeval(0, 0));
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_990), UTC()).toTimeVal() ==
+                   timeval(0, -1));
+
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999_999), UTC()).toTimeVal() ==
+                   timeval(0, -1));
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999), UTC()).toTimeVal() ==
+                   timeval(0, -999_001));
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC()).toTimeVal() ==
+                   timeval(0, -1000));
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), UTC()).toTimeVal() == timeval(-1, 0));
+            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 58), FracSec.from!"usecs"(17), UTC()).toTimeVal() ==
+                   timeval(-1, -999_983));
+        }
+    }
+
+
+    /++
+        Returns a tm which represents this SysTime.
+      +/
+    tm toTM() const nothrow
+    {
+        try
+        {
+            auto dateTime = cast(DateTime)this;
+            tm timeInfo;
+
+            timeInfo.tm_sec = dateTime.second;
+            timeInfo.tm_min = dateTime.minute;
+            timeInfo.tm_hour = dateTime.hour;
+            timeInfo.tm_mday = dateTime.day;
+            timeInfo.tm_mon = dateTime.month - 1;
+            timeInfo.tm_year = dateTime.year - 1900;
+            timeInfo.tm_wday = dateTime.dayOfWeek;
+            timeInfo.tm_yday = dateTime.dayOfYear - 1;
+            timeInfo.tm_isdst = _timezone.dstInEffect(_stdTime);
+
+            version(Posix)
+            {
+                char[] zone = (timeInfo.tm_isdst ? _timezone.dstName : _timezone.stdName).dup;
+                zone ~= "\0";
+
+                timeInfo.tm_gmtoff = cast(int)convert!("hnsecs", "seconds")(adjTime - _stdTime);
+                timeInfo.tm_zone = zone.ptr;
+            }
+
+            return timeInfo;
+        }
+        catch(Exception e)
+            assert(0, "Either DateTime's constructor threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            version(Posix)
+            {
+                scope(exit) clearTZEnvVar();
+                setTZEnvVar("America/Los_Angeles");
+            }
+
+            {
+                auto timeInfo = SysTime(DateTime(1970, 1, 1)).toTM();
+
+                assertPred!"=="(timeInfo.tm_sec, 0);
+                assertPred!"=="(timeInfo.tm_min, 0);
+                assertPred!"=="(timeInfo.tm_hour, 0);
+                assertPred!"=="(timeInfo.tm_mday, 1);
+                assertPred!"=="(timeInfo.tm_mon, 0);
+                assertPred!"=="(timeInfo.tm_year, 70);
+                assertPred!"=="(timeInfo.tm_wday, 4);
+                assertPred!"=="(timeInfo.tm_yday, 0);
+
+                version(Posix)
+                    assertPred!"=="(timeInfo.tm_isdst, 0);
+                else version(Windows)
+                    assert(timeInfo.tm_isdst == 0 || timeInfo.tm_isdst == 1);
+
+                version(Posix)
+                {
+                    assertPred!"=="(timeInfo.tm_gmtoff, -8 * 60 * 60);
+                    assertPred!"=="(to!string(timeInfo.tm_zone), "PST");
+                }
+            }
+
+            {
+                auto timeInfo = SysTime(DateTime(2010, 7, 4, 12, 15, 7), FracSec.from!"hnsecs"(15)).toTM();
+
+                assertPred!"=="(timeInfo.tm_sec, 7);
+                assertPred!"=="(timeInfo.tm_min, 15);
+                assertPred!"=="(timeInfo.tm_hour, 12);
+                assertPred!"=="(timeInfo.tm_mday, 4);
+                assertPred!"=="(timeInfo.tm_mon, 6);
+                assertPred!"=="(timeInfo.tm_year, 110);
+                assertPred!"=="(timeInfo.tm_wday, 0);
+                assertPred!"=="(timeInfo.tm_yday, 184);
+
+                version(Posix)
+                    assertPred!"=="(timeInfo.tm_isdst, 1);
+                else version(Windows)
+                    assert(timeInfo.tm_isdst == 0 || timeInfo.tm_isdst == 1);
+
+                version(Posix)
+                {
+                    assertPred!"=="(timeInfo.tm_gmtoff, -7 * 60 * 60);
+                    assertPred!"=="(to!string(timeInfo.tm_zone), "PDT");
+                }
+            }
+        }
+    }
+
+
+    /++
+        Adds the given number of years or months to this SysTime. A negative
+        number will subtract.
+
+        Note that if day overflow is allowed, and the date with the adjusted
+        year/month overflows the number of days in the new month, then the month
+        will be incremented by one, and the days set to the number of days overflowed.
+        (e.g. if the day were 31 and the new month were June, then the month would
+        be incremented to July, and the new day would be 1). If day overflow is not
+        allowed, then the day will be set to the last valid day in the month
+        (e.g. June 31st would become June 30th).
+
+        Params:
+            units         = The type of units to add ("years" or "months").
+            value         = The number of months or years to add to this SysTime.
+            allowOverflow = Whether the days should be allowed to overflow, causing
+                            the month to increment.
+
+        Examples:
+--------------------
+auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
+st1.add!"months"(11);
+assert(st1 == SysTime(DateTime(2010, 12, 1, 12, 30, 33)));
+
+auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
+st2.add!"months"(-11);
+assert(st2 == SysTime(DateTime(2009, 2, 1, 12, 30, 33)));
+
+auto st3 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
+st3.add!"years"(1);
+assert(st3 == SysTime(DateTime(2001, 3, 1, 12, 30, 33)));
+
+auto st4 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
+st4.add!"years"(1, AllowDayOverflow.no);
+assert(st4 == SysTime(DateTime(2001, 2, 28, 12, 30, 33)));
+--------------------
+      +/
+    ref SysTime add(string units)(long years, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
+        if(units == "years" ||
+           units == "months")
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.add!units(years, allowOverflow);
+        days = date.dayOfGregorianCal - 1;
+
+        if(days < 0)
+        {
+            hnsecs -= convert!("hours", "hnsecs")(24);
+            ++days;
+        }
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
+
+        adjTime = newDaysHNSecs + hnsecs;
+
+        return this;
+    }
+
+    //Test add!"years"() with AllowDayOverlow.yes
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"years"(7);
+                assertPred!"=="(sysTime, SysTime(Date(2006, 7, 6)));
+                sysTime.add!"years"(-9);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
+                sysTime.add!"years"(7);
+                assertPred!"=="(sysTime, SysTime(DateTime(2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+                sysTime.add!"years"(-9);
+                assertPred!"=="(sysTime, SysTime(DateTime(1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(2000, 2, 29, 0, 7, 2), FracSec.from!"usecs"(1207));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 3, 1, 0, 7, 2), FracSec.from!"usecs"(1207)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"years"(-7);
+                assertPred!"=="(sysTime, SysTime(Date(-2006, 7, 6)));
+                sysTime.add!"years"(9);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
+                sysTime.add!"years"(-7);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+                sysTime.add!"years"(9);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2000, 2, 29, 3, 3, 3), FracSec.from!"hnsecs"(3));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 3, 1, 3, 3, 3), FracSec.from!"hnsecs"(3)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(4, 7, 6));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 7, 6)));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 7, 6));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 6)));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 7, 6));
+                sysTime.add!"years"(-8);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+                sysTime.add!"years"(8);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 7, 6));
+                sysTime.add!"years"(8);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+                sysTime.add!"years"(-8);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 2, 29));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(Date(1, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 2, 29));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"years"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"years"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 3, 1, 5, 5, 5), FracSec.from!"msecs"(555)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1, 3, 1, 5, 5, 5), FracSec.from!"msecs"(555)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.add!"years"(4)));
+            //static assert(!__traits(compiles, ist.add!"years"(4)));
+
+            //Verify Examples.
+            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
+            st1.add!"months"(11);
+            assert(st1 == SysTime(DateTime(2010, 12, 1, 12, 30, 33)));
+
+            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
+            st2.add!"months"(-11);
+            assert(st2 == SysTime(DateTime(2009, 2, 1, 12, 30, 33)));
+
+            auto st3 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
+            st3.add!"years"(1);
+            assert(st3 == SysTime(DateTime(2001, 3, 1, 12, 30, 33)));
+
+            auto st4 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
+            st4.add!"years"(1, AllowDayOverflow.no);
+            assert(st4 == SysTime(DateTime(2001, 2, 28, 12, 30, 33)));
+        }
+    }
+
+    //Test add!"years"() with AllowDayOverlow.no
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"years"(7, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2006, 7, 6)));
+                sysTime.add!"years"(-9, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
+                sysTime.add!"years"(7, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+                sysTime.add!"years"(-9, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(2000, 2, 29, 0, 7, 2), FracSec.from!"usecs"(1207));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"years"(-7, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2006, 7, 6)));
+                sysTime.add!"years"(9, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
+                sysTime.add!"years"(-7, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+                sysTime.add!"years"(9, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2000, 2, 29, 3, 3, 3), FracSec.from!"hnsecs"(3));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(4, 7, 6));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 7, 6)));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 7, 6));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 6)));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 7, 6));
+                sysTime.add!"years"(-8, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+                sysTime.add!"years"(8, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 7, 6));
+                sysTime.add!"years"(8, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
+                sysTime.add!"years"(-8, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 2, 29));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 2, 29));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"years"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"years"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
+                sysTime.add!"years"(-5);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+                sysTime.add!"years"(5);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
+                sysTime.add!"years"(5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 2, 28, 5, 5, 5), FracSec.from!"msecs"(555)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
+                sysTime.add!"years"(-5, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1, 2, 28, 5, 5, 5), FracSec.from!"msecs"(555)));
+            }
+        }
+    }
+
+    //Test add!"months"() with AllowDayOverlow.yes
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(3);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.add!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(6);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 6)));
+                sysTime.add!"months"(-6);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(27);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 10, 6)));
+                sysTime.add!"months"(-28);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 5, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.add!"months"(12);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.add!"months"(12);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 31));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 8, 31));
+                sysTime.add!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
+                sysTime.add!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.add!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 31)));
+                sysTime.add!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 3)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 3, 2)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 3, 3)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.add!"months"(3);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.add!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(2000, 3, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 1, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(2001, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(2000, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(3);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
+                sysTime.add!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(6);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 1, 6)));
+                sysTime.add!"months"(-6);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(-27);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 4, 6)));
+                sysTime.add!"months"(28);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 5, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.add!"months"(-12);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.add!"months"(-12);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 3, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 31));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1998, 8, 31));
+                sysTime.add!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 10, 1)));
+                sysTime.add!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.add!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(-1995, 1, 31)));
+                sysTime.add!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-1995, 3, 3)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-1996, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2002, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 3, 2)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 1, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2001, 12, 31));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 3, 3)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.add!"months"(3);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.add!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 3, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 1, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(1, 1, 1));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(0, 12, 1)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 1, 1));
+                sysTime.add!"months"(-48);
+                assertPred!"=="(sysTime, SysTime(Date(0, 1, 1)));
+                sysTime.add!"months"(48);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.add!"months"(-49);
+                assertPred!"=="(sysTime, SysTime(Date(0, 3, 2)));
+                sysTime.add!"months"(49);
+                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.add!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(Date(-3, 3, 3)));
+                sysTime.add!"months"(85);
+                assertPred!"=="(sysTime, SysTime(Date(4, 4, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
+                sysTime.add!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+                sysTime.add!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.add!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 3, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.add!"months"(85);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 3, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.add!"months"(85);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 5, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.add!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.add!"months"(4)));
+            //static assert(!__traits(compiles, ist.add!"months"(4)));
+
+            //Verify Examples.
+            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30 ,33));
+            st1.add!"months"(1);
+            assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 30 ,33)));
+
+            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30 ,33));
+            st2.add!"months"(-1);
+            assert(st2 == SysTime(DateTime(2009, 12, 1, 12, 30 ,33)));
+
+            auto st3 = SysTime(DateTime(1999, 1, 29, 12, 30 ,33));
+            st3.add!"months"(1);
+            assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 30 ,33)));
+
+            auto st4 = SysTime(DateTime(1999, 1, 29, 12, 30 ,33));
+            st4.add!"months"(1, AllowDayOverflow.no);
+            assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 30 ,33)));
+        }
+    }
+
+    //Test add!"months"() with AllowDayOverlow.no
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.add!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 6)));
+                sysTime.add!"months"(-6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.add!"months"(27, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 10, 6)));
+                sysTime.add!"months"(-28, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 4, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.add!"months"(12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.add!"months"(12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 31));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 8, 31));
+                sysTime.add!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
+                sysTime.add!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 8, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.add!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 31)));
+                sysTime.add!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 12, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2001, 2, 28)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.add!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.add!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1998, 12, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(2001, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
+                sysTime.add!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 1, 6)));
+                sysTime.add!"months"(-6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.add!"months"(-27, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 4, 6)));
+                sysTime.add!"months"(28, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.add!"months"(-12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.add!"months"(-12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 31));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 9, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1998, 8, 31));
+                sysTime.add!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 9, 30)));
+                sysTime.add!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 8, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.add!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1995, 1, 31)));
+                sysTime.add!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1995, 2, 28)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2002, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2002, 12, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2001, 12, 31));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.add!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.add!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 12, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.add!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.add!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(1, 1, 1));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(0, 12, 1)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 1, 1));
+                sysTime.add!"months"(-48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(0, 1, 1)));
+                sysTime.add!"months"(48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.add!"months"(-49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(0, 2, 29)));
+                sysTime.add!"months"(49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.add!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-3, 2, 28)));
+                sysTime.add!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
+                sysTime.add!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+                sysTime.add!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.add!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 2, 28, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.add!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 28, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.add!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.add!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+        }
+    }
+
+
+    /++
+        Adds the given number of years to this SysTime. A negative number will
+        subtract.
+
+        For years, because they are the largest unit in SysTime, there is no
+        difference between adding or rolling.
+
+        Params:
+            years         = The number of years to add to this SysTime.
+            allowOverflow = Whether the days should be allowed to overflow,
+                            causing the month to increment.
+      +/
+    /+ref SysTime+/ void roll(string units)(long years, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
+        if(units == "years")
+    {
+        add!"years"(years, allowOverflow);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.roll!"years"(4)));
+            static assert(!__traits(compiles, cst.roll!"years"(4)));
+            //static assert(!__traits(compiles, ist.roll!"years"(4)));
+        }
+    }
+
+
+    /++
+        Adds the given number of months to this SysTime. A negative number will
+        subtract.
+
+        The difference between rolling and adding is that rolling does not affect
+        larger units. So, if you roll the SysTime 12 months, you get the exact
+        same SysTime. However, the days can still be affected due to the differing
+        number of days in each month.
+
+        Params:
+            months        = The number of months to add to this SysTime.
+            allowOverflow = Whether the days should be allowed to overflow,
+                            causing the month to increment.
+
+        Examples:
+--------------------
+auto st1 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
+st1.roll!"months"(1);
+assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 33, 33)));
+
+auto st2 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
+st2.roll!"months"(-1);
+assert(st2 == SysTime(DateTime(2010, 12, 1, 12, 33, 33)));
+
+auto st3 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
+st3.roll!"months"(1);
+assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 33, 33)));
+
+auto st4 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
+st4.roll!"months"(1, AllowDayOverflow.no);
+assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 33, 33)));
+--------------------
+      +/
+    /+ref SysTime+/ void roll(string units)(long months, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
+        if(units == "months")
+    {
+        auto hnsecs = adjTime;
+        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --days;
+        }
+
+        auto date = Date(cast(int)days);
+        date.roll!"months"(months, allowOverflow);
+        days = date.dayOfGregorianCal - 1;
+
+        if(days < 0)
+        {
+            hnsecs -= convert!("hours", "hnsecs")(24);
+            ++days;
+        }
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    //Test roll!"months"() with AllowDayOverlow.yes
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(3);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.roll!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(6);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 6)));
+                sysTime.roll!"months"(-6);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(27);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.roll!"months"(-28);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 5, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.roll!"months"(12);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.roll!"months"(12);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 31));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 8, 31));
+                sysTime.roll!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 10, 1)));
+                sysTime.roll!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.roll!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 31)));
+                sysTime.roll!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.roll!"months"(3);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.roll!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(1998, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(1998, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(3);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
+                sysTime.roll!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(6);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 6)));
+                sysTime.roll!"months"(-6);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(-27);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 6)));
+                sysTime.roll!"months"(28);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 5, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.roll!"months"(-12);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.roll!"months"(-12);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 31));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1998, 8, 31));
+                sysTime.roll!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 10, 1)));
+                sysTime.roll!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.roll!"months"(13);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 31)));
+                sysTime.roll!"months"(-13);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2002, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-2002, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-2002, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2001, 12, 31));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 3, 3)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 1, 3)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007));
+                sysTime.roll!"months"(3);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007)));
+                sysTime.roll!"months"(-4);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(1, 1, 1));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1, 12, 1)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 1, 1));
+                sysTime.roll!"months"(-48);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+                sysTime.roll!"months"(48);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.roll!"months"(-49);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 2)));
+                sysTime.roll!"months"(49);
+                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.roll!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 2)));
+                sysTime.roll!"months"(85);
+                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1, 1, 1));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 12, 1)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 1, 1));
+                sysTime.roll!"months"(-48);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
+                sysTime.roll!"months"(48);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 3, 31));
+                sysTime.roll!"months"(-49);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 2)));
+                sysTime.roll!"months"(49);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 4, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 3, 31));
+                sysTime.roll!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 2)));
+                sysTime.roll!"months"(85);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 4, 2)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
+                sysTime.roll!"months"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+                sysTime.roll!"months"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.roll!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 2, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.roll!"months"(85);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 2, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.roll!"months"(85);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 5, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.roll!"months"(-85);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"months"(4)));
+            //static assert(!__traits(compiles, ist.roll!"months"(4)));
+
+            //Verify Examples.
+            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
+            st1.roll!"months"(1);
+            assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 33, 33)));
+
+            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
+            st2.roll!"months"(-1);
+            assert(st2 == SysTime(DateTime(2010, 12, 1, 12, 33, 33)));
+
+            auto st3 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
+            st3.roll!"months"(1);
+            assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 33, 33)));
+
+            auto st4 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
+            st4.roll!"months"(1, AllowDayOverflow.no);
+            assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 33, 33)));
+        }
+    }
+
+    //Test roll!"months"() with AllowDayOverlow.no
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.roll!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 6)));
+                sysTime.roll!"months"(-6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"months"(27, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
+                sysTime.roll!"months"(-28, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 5, 31));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 4, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.roll!"months"(12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 29));
+                sysTime.roll!"months"(12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 31));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 8, 31));
+                sysTime.roll!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 30)));
+                sysTime.roll!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 8, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.roll!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 31)));
+                sysTime.roll!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1997, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1998, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1998, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.roll!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.roll!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1998, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1998, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
+                sysTime.roll!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 6)));
+                sysTime.roll!"months"(-6, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"months"(-27, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 6)));
+                sysTime.roll!"months"(28, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 5, 31));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.roll!"months"(-12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 29));
+                sysTime.roll!"months"(-12, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 31));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 9, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1998, 8, 31));
+                sysTime.roll!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 30)));
+                sysTime.roll!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1998, 8, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.roll!"months"(13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 31)));
+                sysTime.roll!"months"(-13, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1997, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2002, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2002, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2002, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2001, 12, 31));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 2, 28)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-2001, 12, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
+                sysTime.roll!"months"(3, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+                sysTime.roll!"months"(-4, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
+                sysTime.roll!"months"(14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+                sysTime.roll!"months"(-14, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(1, 1, 1));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1, 12, 1)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 1, 1));
+                sysTime.roll!"months"(-48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+                sysTime.roll!"months"(48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.roll!"months"(-49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 2, 29)));
+                sysTime.roll!"months"(49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(4, 3, 31));
+                sysTime.roll!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 2, 29)));
+                sysTime.roll!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1, 1, 1));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 12, 1)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-1, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 1, 1));
+                sysTime.roll!"months"(-48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
+                sysTime.roll!"months"(48, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 3, 31));
+                sysTime.roll!"months"(-49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 2, 29)));
+                sysTime.roll!"months"(49, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-4, 3, 31));
+                sysTime.roll!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 2, 29)));
+                sysTime.roll!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
+                sysTime.roll!"months"(-1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+                sysTime.roll!"months"(1, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.roll!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 2, 29, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.roll!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 29, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
+                sysTime.roll!"months"(85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
+                sysTime.roll!"months"(-85, AllowDayOverflow.no);
+                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
+            }
+        }
+    }
+
+
+    /++
+        Adds the given number of days to this SysTime. A negative number will
+        subtract.
+
+        The difference between rolling and adding is that rolling does not affect
+        larger units. So, if you roll the SysTime one year's worth of days, then
+        you get the exact same SysTime.
+
+        Note that TimeOfDay has no $(D add!"days"()) function because you can add
+        days to a SysTime by adding a duration to it.
+
+        Params:
+            days = The number of days to add to this SysTime.
+
+        Examples:
+--------------------
+auto st = SysTime(DateTime(2010, 1, 1, 11, 23, 12));
+st.roll!"days"(1);
+assert(st == SysTime(DateTime(2010, 1, 2, 11, 23, 12)));
+st.roll!"days"(365);
+assert(st == SysTime(DateTime(2010, 1, 26, 11, 23, 12)));
+st.roll!"days"(-32);
+assert(st == SysTime(DateTime(2010, 1, 25, 11, 23, 12)));
+--------------------
+      +/
+    /+ref SysTime+/ void roll(string units)(long days) nothrow
+        if(units == "days")
+    {
+        auto hnsecs = adjTime;
+        auto gdays = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+        if(hnsecs < 0)
+        {
+            hnsecs += convert!("hours", "hnsecs")(24);
+            --gdays;
+        }
+
+        auto date = Date(cast(int)gdays);
+        date.roll!"days"(days);
+        gdays = date.dayOfGregorianCal - 1;
+
+        if(gdays < 0)
+        {
+            hnsecs -= convert!("hours", "hnsecs")(24);
+            ++gdays;
+        }
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(gdays);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            {
+                auto sysTime = SysTime(Date(1999, 2, 28));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(2000, 2, 28));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 6, 30));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 31));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 1, 1));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 31)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"days"(9);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 15)));
+                sysTime.roll!"days"(-11);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 4)));
+                sysTime.roll!"days"(30);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 3)));
+                sysTime.roll!"days"(-3);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 7, 6));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 30)));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+                sysTime.roll!"days"(366);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 31)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 17)));
+                sysTime.roll!"days"(-1096);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(1999, 2, 6));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 7)));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 6)));
+                sysTime.roll!"days"(366);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 8)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 10)));
+                sysTime.roll!"days"(-1096);
+                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 2, 28, 7, 9, 2), FracSec.from!"usecs"(234578));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 1, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 28, 7, 9, 2), FracSec.from!"usecs"(234578)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1999, 7, 6, 7, 9, 2), FracSec.from!"usecs"(234578));
+                sysTime.roll!"days"(9);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 7, 15, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-11);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 7, 4, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(30);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 7, 3, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-3);
+                assertPred!"=="(sysTime, SysTime(DateTime(1999, 7, 31, 7, 9, 2), FracSec.from!"usecs"(234578)));
+            }
+
+            //Test B.C.
+            {
+                auto sysTime = SysTime(Date(-1999, 2, 28));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-2000, 2, 28));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 6, 30));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 30)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 31));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 1)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 1, 1));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 31)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 1)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"days"(9);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 15)));
+                sysTime.roll!"days"(-11);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 4)));
+                sysTime.roll!"days"(30);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 3)));
+                sysTime.roll!"days"(-3);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 31)));
+            }
+
+            {
+                auto sysTime = SysTime(Date(-1999, 7, 6));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 30)));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+                sysTime.roll!"days"(366);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 31)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 17)));
+                sysTime.roll!"days"(-1096);
+                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 2, 28, 7, 9, 2), FracSec.from!"usecs"(234578));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 1, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 28, 7, 9, 2), FracSec.from!"usecs"(234578)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(-1999, 7, 6, 7, 9, 2), FracSec.from!"usecs"(234578));
+                sysTime.roll!"days"(9);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 7, 15, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-11);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 7, 4, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(30);
+                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 7, 3, 7, 9, 2), FracSec.from!"usecs"(234578)));
+                sysTime.roll!"days"(-3);
+            }
+
+            //Test Both
+            {
+                auto sysTime = SysTime(Date(1, 7, 6));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 13)));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 6)));
+                sysTime.roll!"days"(-731);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 19)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(Date(1, 7, 5)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"days"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"days"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 7, 6, 13, 13, 9), FracSec.from!"msecs"(22));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 13, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 6, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(-731);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 19, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 5, 13, 13, 9), FracSec.from!"msecs"(22)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 7, 6, 13, 13, 9), FracSec.from!"msecs"(22));
+                sysTime.roll!"days"(-365);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 7, 13, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(365);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 7, 6, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(-731);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 7, 19, 13, 13, 9), FracSec.from!"msecs"(22)));
+                sysTime.roll!"days"(730);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 7, 5, 13, 13, 9), FracSec.from!"msecs"(22)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"days"(4)));
+            //static assert(!__traits(compiles, ist.roll!"days"(4)));
+
+            //Verify Examples.
+            auto st = SysTime(DateTime(2010, 1, 1, 11, 23, 12));
+            st.roll!"days"(1);
+            assert(st == SysTime(DateTime(2010, 1, 2, 11, 23, 12)));
+            st.roll!"days"(365);
+            assert(st == SysTime(DateTime(2010, 1, 26, 11, 23, 12)));
+            st.roll!"days"(-32);
+            assert(st == SysTime(DateTime(2010, 1, 25, 11, 23, 12)));
+        }
+    }
+
+
+
+    /++
+        Add hours to the time of day. Negative values will subtract.
+
+        The difference between rolling and adding is that rolling does not
+        affect larger units. So, if you roll the SysTime 24 hours, you get
+        the exact same SysTime.
+
+        Note that SysTime has no $(D add!"hours"()), $(D add!"minutes"()), or
+        $(D add!"seconds"()) function because you can add those units to
+        a SysTime by adding a duration to it.
+
+        Params:
+            hours = The number of hours to add to this SysTime.
+
+        Examples:
+--------------------
+auto st1 = SysTime(DateTime(2010, 7, 4, 12, 0, 0));
+st1.roll!"hours"(1);
+assert(st1 == SysTime(DateTime(2010, 7, 4, 13, 0, 0)));
+
+auto st2 = SysTime(DateTime(2010, 2, 12, 12, 0, 0));
+st2.roll!"hours"(-1);
+assert(st2 == SysTime(DateTime(2010, 2, 12, 11, 0, 0)));
+
+auto st3 = SysTime(DateTime(2009, 12, 31, 0, 0, 0));
+st3.roll!"minutes"(1);
+assert(st3 == SysTime(DateTime(2009, 12, 31, 0, 1, 0)));
+
+auto st4 = SysTime(DateTime(2010, 1, 1, 0, 0, 0));
+st4.roll!"minutes"(-1);
+assert(st4 == SysTime(DateTime(2010, 1, 1, 0, 59, 0)));
+
+auto st5 = SysTime(DateTime(2009, 12, 31, 0, 0, 0));
+st5.roll!"seconds"(1);
+assert(st5 == SysTime(DateTime(2009, 12, 31, 0, 0, 1)));
+
+auto st6 = SysTime(DateTime(2010, 1, 1, 0, 0, 0));
+st6.roll!"seconds"(-1);
+assert(st6 == SysTime(DateTime(2010, 1, 1, 0, 0, 59)));
+--------------------
+      +/
+    /+ref SysTime+/ void roll(string units)(long value) nothrow
+        if(units == "hours" ||
+           units == "minutes" ||
+           units == "seconds")
+    {
+        try
+        {
+            auto hnsecs = adjTime;
+            auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+            if(hnsecs < 0)
+            {
+                hnsecs += convert!("hours", "hnsecs")(24);
+                --days;
+            }
+
+            immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            immutable second = splitUnitsFromHNSecs!"seconds"(hnsecs);
+
+            auto dateTime = DateTime(Date(cast(int)days), TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second));
+            dateTime.roll!units(value);
+            --days;
+
+            hnsecs += convert!("hours", "hnsecs")(dateTime.hour);
+            hnsecs += convert!("minutes", "hnsecs")(dateTime.minute);
+            hnsecs += convert!("seconds", "hnsecs")(dateTime.second);
+
+            if(days < 0)
+            {
+                hnsecs -= convert!("hours", "hnsecs")(24);
+                ++days;
+            }
+
+            immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
+
+            adjTime = newDaysHNSecs + hnsecs;
+        }
+        catch(Exception e)
+            assert(0, "Either DateTime's constructor or TimeOfDay's constructor threw.");
+    }
+
+    //Test roll!"hours"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, int hours, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"hours"(hours);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 2, SysTime(DateTime(1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 3, SysTime(DateTime(1999, 7, 6, 15, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 4, SysTime(DateTime(1999, 7, 6, 16, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 5, SysTime(DateTime(1999, 7, 6, 17, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 6, SysTime(DateTime(1999, 7, 6, 18, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 7, SysTime(DateTime(1999, 7, 6, 19, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 8, SysTime(DateTime(1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 9, SysTime(DateTime(1999, 7, 6, 21, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 10, SysTime(DateTime(1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 11, SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 12, SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 13, SysTime(DateTime(1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 14, SysTime(DateTime(1999, 7, 6, 2, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 15, SysTime(DateTime(1999, 7, 6, 3, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 16, SysTime(DateTime(1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 17, SysTime(DateTime(1999, 7, 6, 5, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 18, SysTime(DateTime(1999, 7, 6, 6, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 19, SysTime(DateTime(1999, 7, 6, 7, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 20, SysTime(DateTime(1999, 7, 6, 8, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 21, SysTime(DateTime(1999, 7, 6, 9, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 22, SysTime(DateTime(1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 23, SysTime(DateTime(1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 24, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 50, SysTime(DateTime(1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 10_000, SysTime(DateTime(1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -2, SysTime(DateTime(1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -3, SysTime(DateTime(1999, 7, 6, 9, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -4, SysTime(DateTime(1999, 7, 6, 8, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -5, SysTime(DateTime(1999, 7, 6, 7, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -6, SysTime(DateTime(1999, 7, 6, 6, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -7, SysTime(DateTime(1999, 7, 6, 5, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -8, SysTime(DateTime(1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -9, SysTime(DateTime(1999, 7, 6, 3, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -10, SysTime(DateTime(1999, 7, 6, 2, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -11, SysTime(DateTime(1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -12, SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -13, SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -14, SysTime(DateTime(1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -15, SysTime(DateTime(1999, 7, 6, 21, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -16, SysTime(DateTime(1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -17, SysTime(DateTime(1999, 7, 6, 19, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -18, SysTime(DateTime(1999, 7, 6, 18, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -19, SysTime(DateTime(1999, 7, 6, 17, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -20, SysTime(DateTime(1999, 7, 6, 16, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -21, SysTime(DateTime(1999, 7, 6, 15, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -22, SysTime(DateTime(1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -23, SysTime(DateTime(1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -24, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -50, SysTime(DateTime(1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -10_000, SysTime(DateTime(1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 7, 31, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(1999, 7, 31, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 8, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(1999, 8, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 12, 31, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(1999, 12, 31, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(2000, 1, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(2000, 1, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(1999, 2, 28, 23, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(1999, 2, 28, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1999, 3, 2, 0, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(1999, 3, 2, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(2000, 2, 28, 23, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(2000, 2, 28, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(2000, 3, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(2000, 3, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(-1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 2, SysTime(DateTime(-1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 3, SysTime(DateTime(-1999, 7, 6, 15, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 4, SysTime(DateTime(-1999, 7, 6, 16, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 5, SysTime(DateTime(-1999, 7, 6, 17, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 6, SysTime(DateTime(-1999, 7, 6, 18, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 7, SysTime(DateTime(-1999, 7, 6, 19, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 8, SysTime(DateTime(-1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 9, SysTime(DateTime(-1999, 7, 6, 21, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 10, SysTime(DateTime(-1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 11, SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 12, SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 13, SysTime(DateTime(-1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 14, SysTime(DateTime(-1999, 7, 6, 2, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 15, SysTime(DateTime(-1999, 7, 6, 3, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 16, SysTime(DateTime(-1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 17, SysTime(DateTime(-1999, 7, 6, 5, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 18, SysTime(DateTime(-1999, 7, 6, 6, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 19, SysTime(DateTime(-1999, 7, 6, 7, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 20, SysTime(DateTime(-1999, 7, 6, 8, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 21, SysTime(DateTime(-1999, 7, 6, 9, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 22, SysTime(DateTime(-1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 23, SysTime(DateTime(-1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 24, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(-1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 50, SysTime(DateTime(-1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), 10_000, SysTime(DateTime(-1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(-1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -2, SysTime(DateTime(-1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -3, SysTime(DateTime(-1999, 7, 6, 9, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -4, SysTime(DateTime(-1999, 7, 6, 8, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -5, SysTime(DateTime(-1999, 7, 6, 7, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -6, SysTime(DateTime(-1999, 7, 6, 6, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -7, SysTime(DateTime(-1999, 7, 6, 5, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -8, SysTime(DateTime(-1999, 7, 6, 4, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -9, SysTime(DateTime(-1999, 7, 6, 3, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -10, SysTime(DateTime(-1999, 7, 6, 2, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -11, SysTime(DateTime(-1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -12, SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -13, SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -14, SysTime(DateTime(-1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -15, SysTime(DateTime(-1999, 7, 6, 21, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -16, SysTime(DateTime(-1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -17, SysTime(DateTime(-1999, 7, 6, 19, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -18, SysTime(DateTime(-1999, 7, 6, 18, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -19, SysTime(DateTime(-1999, 7, 6, 17, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -20, SysTime(DateTime(-1999, 7, 6, 16, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -21, SysTime(DateTime(-1999, 7, 6, 15, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -22, SysTime(DateTime(-1999, 7, 6, 14, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -23, SysTime(DateTime(-1999, 7, 6, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -24, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(-1999, 7, 6, 11, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -50, SysTime(DateTime(-1999, 7, 6, 10, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(45)), -10_000, SysTime(DateTime(-1999, 7, 6, 20, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(-1999, 7, 6, 1, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(-1999, 7, 6, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), 0, SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 23, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(-1999, 7, 6, 22, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-1999, 7, 31, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(-1999, 7, 31, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-1999, 8, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(-1999, 8, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-2001, 12, 31, 23, 30, 33), FracSec.from!"msecs"(45)), 1, SysTime(DateTime(-2001, 12, 31, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-2000, 1, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -1, SysTime(DateTime(-2000, 1, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-2001, 2, 28, 23, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(-2001, 2, 28, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-2001, 3, 2, 0, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(-2001, 3, 2, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            TestST(SysTime(DateTime(-2000, 2, 28, 23, 30, 33), FracSec.from!"msecs"(45)), 25, SysTime(DateTime(-2000, 2, 28, 0, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(-2000, 3, 1, 0, 30, 33), FracSec.from!"msecs"(45)), -25, SysTime(DateTime(-2000, 3, 1, 23, 30, 33), FracSec.from!"msecs"(45)));
+
+            //Test Both
+            TestST(SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"msecs"(45)), 17_546, SysTime(DateTime(-1, 1, 1, 13, 30, 33), FracSec.from!"msecs"(45)));
+            TestST(SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"msecs"(45)), -17_546, SysTime(DateTime(1, 1, 1, 11, 30, 33), FracSec.from!"msecs"(45)));
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"hours"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"hours"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"hours"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"hours"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"hours"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"hours"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"hours"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 0, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"hours"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"hours"(4)));
+            //static assert(!__traits(compiles, ist.roll!"hours"(4)));
+
+            //Verify Examples.
+            auto st1 = SysTime(DateTime(2010, 7, 4, 12, 0, 0));
+            st1.roll!"hours"(1);
+            assert(st1 == SysTime(DateTime(2010, 7, 4, 13, 0, 0)));
+
+            auto st2 = SysTime(DateTime(2010, 2, 12, 12, 0, 0));
+            st2.roll!"hours"(-1);
+            assert(st2 == SysTime(DateTime(2010, 2, 12, 11, 0, 0)));
+
+            auto st3 = SysTime(DateTime(2009, 12, 31, 0, 0, 0));
+            st3.roll!"minutes"(1);
+            assert(st3 == SysTime(DateTime(2009, 12, 31, 0, 1, 0)));
+
+            auto st4 = SysTime(DateTime(2010, 1, 1, 0, 0, 0));
+            st4.roll!"minutes"(-1);
+            assert(st4 == SysTime(DateTime(2010, 1, 1, 0, 59, 0)));
+
+            auto st5 = SysTime(DateTime(2009, 12, 31, 0, 0, 0));
+            st5.roll!"seconds"(1);
+            assert(st5 == SysTime(DateTime(2009, 12, 31, 0, 0, 1)));
+
+            auto st6 = SysTime(DateTime(2010, 1, 1, 0, 0, 0));
+            st6.roll!"seconds"(-1);
+            assert(st6 == SysTime(DateTime(2010, 1, 1, 0, 0, 59)));
+        }
+    }
+
+    //Test roll!"minutes"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, int minutes, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"minutes"(minutes);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 2, SysTime(DateTime(1999, 7, 6, 12, 32, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 3, SysTime(DateTime(1999, 7, 6, 12, 33, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 4, SysTime(DateTime(1999, 7, 6, 12, 34, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 5, SysTime(DateTime(1999, 7, 6, 12, 35, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 10, SysTime(DateTime(1999, 7, 6, 12, 40, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 15, SysTime(DateTime(1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 29, SysTime(DateTime(1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 30, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 45, SysTime(DateTime(1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 60, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 75, SysTime(DateTime(1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 90, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 100, SysTime(DateTime(1999, 7, 6, 12, 10, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 689, SysTime(DateTime(1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 690, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 691, SysTime(DateTime(1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 960, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1439, SysTime(DateTime(1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1440, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1441, SysTime(DateTime(1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 2880, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -2, SysTime(DateTime(1999, 7, 6, 12, 28, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -3, SysTime(DateTime(1999, 7, 6, 12, 27, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -4, SysTime(DateTime(1999, 7, 6, 12, 26, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -5, SysTime(DateTime(1999, 7, 6, 12, 25, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -10, SysTime(DateTime(1999, 7, 6, 12, 20, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -15, SysTime(DateTime(1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -29, SysTime(DateTime(1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -30, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -45, SysTime(DateTime(1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -60, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -75, SysTime(DateTime(1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -90, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -100, SysTime(DateTime(1999, 7, 6, 12, 50, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -749, SysTime(DateTime(1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -750, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -751, SysTime(DateTime(1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -960, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1439, SysTime(DateTime(1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1440, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1441, SysTime(DateTime(1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -2880, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1999, 7, 6, 11, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1999, 7, 6, 11, 58, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1999, 7, 6, 0, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1999, 7, 6, 0, 59, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1999, 7, 5, 23, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1999, 7, 5, 23, 58, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(1998, 12, 31, 23, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(1998, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(1998, 12, 31, 23, 58, 33), FracSec.from!"usecs"(7203)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 2, SysTime(DateTime(-1999, 7, 6, 12, 32, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 3, SysTime(DateTime(-1999, 7, 6, 12, 33, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 4, SysTime(DateTime(-1999, 7, 6, 12, 34, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 5, SysTime(DateTime(-1999, 7, 6, 12, 35, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 10, SysTime(DateTime(-1999, 7, 6, 12, 40, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 15, SysTime(DateTime(-1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 29, SysTime(DateTime(-1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 30, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 45, SysTime(DateTime(-1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 60, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 75, SysTime(DateTime(-1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 90, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 100, SysTime(DateTime(-1999, 7, 6, 12, 10, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 689, SysTime(DateTime(-1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 690, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 691, SysTime(DateTime(-1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 960, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1439, SysTime(DateTime(-1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1440, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 1441, SysTime(DateTime(-1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), 2880, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -2, SysTime(DateTime(-1999, 7, 6, 12, 28, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -3, SysTime(DateTime(-1999, 7, 6, 12, 27, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -4, SysTime(DateTime(-1999, 7, 6, 12, 26, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -5, SysTime(DateTime(-1999, 7, 6, 12, 25, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -10, SysTime(DateTime(-1999, 7, 6, 12, 20, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -15, SysTime(DateTime(-1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -29, SysTime(DateTime(-1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -30, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -45, SysTime(DateTime(-1999, 7, 6, 12, 45, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -60, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -75, SysTime(DateTime(-1999, 7, 6, 12, 15, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -90, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -100, SysTime(DateTime(-1999, 7, 6, 12, 50, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -749, SysTime(DateTime(-1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -750, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -751, SysTime(DateTime(-1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -960, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1439, SysTime(DateTime(-1999, 7, 6, 12, 31, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1440, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -1441, SysTime(DateTime(-1999, 7, 6, 12, 29, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)), -2880, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-1999, 7, 6, 12, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-1999, 7, 6, 12, 59, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-1999, 7, 6, 11, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 11, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-1999, 7, 6, 11, 58, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-1999, 7, 6, 0, 1, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-1999, 7, 6, 0, 59, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-1999, 7, 5, 23, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-1999, 7, 5, 23, 58, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), 1, SysTime(DateTime(-2000, 12, 31, 23, 0, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), 0, SysTime(DateTime(-2000, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 33), FracSec.from!"usecs"(7203)), -1, SysTime(DateTime(-2000, 12, 31, 23, 58, 33), FracSec.from!"usecs"(7203)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), -1, SysTime(DateTime(1, 1, 1, 0, 59, 0)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 0)), 1, SysTime(DateTime(0, 12, 31, 23, 0, 0)));
+
+            TestST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), -1, SysTime(DateTime(0, 1, 1, 0, 59, 0)));
+            TestST(SysTime(DateTime(-1, 12, 31, 23, 59, 0)), 1, SysTime(DateTime(-1, 12, 31, 23, 0, 0)));
+
+            TestST(SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"usecs"(7203)), 1_052_760, SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"usecs"(7203)), -1_052_760, SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"usecs"(7203)));
+
+            TestST(SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"usecs"(7203)), 1_052_782, SysTime(DateTime(-1, 1, 1, 11, 52, 33), FracSec.from!"usecs"(7203)));
+            TestST(SysTime(DateTime(1, 1, 1, 13, 52, 33), FracSec.from!"usecs"(7203)), -1_052_782, SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"usecs"(7203)));
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"minutes"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 59, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"minutes"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"minutes"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"minutes"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"minutes"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 0, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"minutes"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"minutes"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 0, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"minutes"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"minutes"(4)));
+            //static assert(!__traits(compiles, ist.roll!"minutes"(4)));
+        }
+    }
+
+    //Test roll!"seconds"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, int seconds, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"seconds"(seconds);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 35), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3, SysTime(DateTime(1999, 7, 6, 12, 30, 36), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 4, SysTime(DateTime(1999, 7, 6, 12, 30, 37), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 5, SysTime(DateTime(1999, 7, 6, 12, 30, 38), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 43), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 15, SysTime(DateTime(1999, 7, 6, 12, 30, 48), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26, SysTime(DateTime(1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 27, SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 30, SysTime(DateTime(1999, 7, 6, 12, 30, 3), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 59, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 60, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 61, SysTime(DateTime(1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1766, SysTime(DateTime(1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1767, SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1768, SysTime(DateTime(1999, 7, 6, 12, 30, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2007, SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3599, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3600, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3601, SysTime(DateTime(1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 7200, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 31), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -3, SysTime(DateTime(1999, 7, 6, 12, 30, 30), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -4, SysTime(DateTime(1999, 7, 6, 12, 30, 29), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -5, SysTime(DateTime(1999, 7, 6, 12, 30, 28), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 23), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -15, SysTime(DateTime(1999, 7, 6, 12, 30, 18), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33, SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -34, SysTime(DateTime(1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -35, SysTime(DateTime(1999, 7, 6, 12, 30, 58), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -59, SysTime(DateTime(1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -60, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -61, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 0, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 0, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 0, 0, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 0, 0, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 5, 23, 59, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 5, 23, 59, 58), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1998, 12, 31, 23, 59, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1998, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1998, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1998, 12, 31, 23, 59, 58), FracSec.from!"msecs"(274)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 35), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3, SysTime(DateTime(-1999, 7, 6, 12, 30, 36), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 4, SysTime(DateTime(-1999, 7, 6, 12, 30, 37), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 5, SysTime(DateTime(-1999, 7, 6, 12, 30, 38), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 43), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 15, SysTime(DateTime(-1999, 7, 6, 12, 30, 48), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26, SysTime(DateTime(-1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 27, SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 30, SysTime(DateTime(-1999, 7, 6, 12, 30, 3), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 59, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 60, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 61, SysTime(DateTime(-1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1766, SysTime(DateTime(-1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1767, SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1768, SysTime(DateTime(-1999, 7, 6, 12, 30, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2007, SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3599, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3600, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 3601, SysTime(DateTime(-1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 7200, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 31), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -3, SysTime(DateTime(-1999, 7, 6, 12, 30, 30), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -4, SysTime(DateTime(-1999, 7, 6, 12, 30, 29), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -5, SysTime(DateTime(-1999, 7, 6, 12, 30, 28), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 23), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -15, SysTime(DateTime(-1999, 7, 6, 12, 30, 18), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33, SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -34, SysTime(DateTime(-1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -35, SysTime(DateTime(-1999, 7, 6, 12, 30, 58), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -59, SysTime(DateTime(-1999, 7, 6, 12, 30, 34), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -60, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -61, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 0, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 0, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 0, 0, 1), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 0, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 0, 0, 59), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 5, 23, 59, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 5, 23, 59, 59), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 5, 23, 59, 58), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-2000, 12, 31, 23, 59, 0), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-2000, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-2000, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-2000, 12, 31, 23, 59, 58), FracSec.from!"msecs"(274)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1, 1, 1, 0, 0, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 0), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(0, 1, 1, 0, 0, 59), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1, 12, 31, 23, 59, 59), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1, 12, 31, 23, 59, 0), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"msecs"(274)), 63_165_600L, SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"msecs"(274)), -63_165_600L, SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"msecs"(274)));
+
+            TestST(SysTime(DateTime(-1, 1, 1, 11, 30, 33), FracSec.from!"msecs"(274)), 63_165_617L, SysTime(DateTime(-1, 1, 1, 11, 30, 50), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1, 1, 1, 13, 30, 50), FracSec.from!"msecs"(274)), -63_165_617L, SysTime(DateTime(1, 1, 1, 13, 30, 33), FracSec.from!"msecs"(274)));
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"seconds"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 59), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"seconds"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"seconds"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 59), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"seconds"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0));
+                sysTime.roll!"seconds"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 0), FracSec.from!"hnsecs"(0)));
+                sysTime.roll!"seconds"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            }
+
+            {
+                auto sysTime = SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+                sysTime.roll!"seconds"(1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 0), FracSec.from!"hnsecs"(9_999_999)));
+                sysTime.roll!"seconds"(-1);
+                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            }
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"seconds"(4)));
+            //static assert(!__traits(compiles, ist.roll!"seconds"(4)));
+        }
+    }
+
+
+    /++
+        Add to the fractional seconds of the time of day. Negative values will
+        subtract.
+
+        The difference between rolling and adding is that rolling does not affect
+        larger units. So, if you roll the SysTime 1 second, you get the exact same
+        SysTime.
+
+        Note that SysTime has no $(D add!"msecs"()), $(D add!"usecs"()), or
+        $(D add!"hnsecs"()) function because you can add those units to
+        a SysTime by adding a duration to it.
+
+        Params:
+            units = The units to add to this SysTime.
+            value = The number of units to add to this SysTime.
+      +/
+    /+ref SysTime+/ void roll(string units)(long value) nothrow
+        if(units == "msecs" ||
+           units == "usecs" ||
+           units == "hnsecs")
+    {
+        auto hnsecs = adjTime;
+        immutable days = splitUnitsFromHNSecs!"days"(hnsecs);
+        immutable negative = hnsecs < 0;
+
+        if(negative)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        immutable seconds = splitUnitsFromHNSecs!"seconds"(hnsecs);
+
+        hnsecs += convert!(units, "hnsecs")(value);
+        hnsecs %= convert!("seconds", "hnsecs")(1);
+
+        if(hnsecs < 0)
+            hnsecs += convert!("seconds", "hnsecs")(1);
+
+        hnsecs += convert!("seconds", "hnsecs")(seconds);
+
+        if(negative)
+            hnsecs -= convert!("hours", "hnsecs")(24);
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+
+    //Test roll!"msecs"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, int milliseconds, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"msecs"(milliseconds);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(276)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(284)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(374)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_727, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(1)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1_766_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1_766_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(272)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(264)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(174)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1_833_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1_833_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(276)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(284)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(374)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 26_727, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(1)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1_766_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), 1_766_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(272)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(264)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(174)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -33_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1_833_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(274)), -1_833_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(999)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(1)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), -1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(999)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), -2, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(998)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), -1000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), -2000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(0)), -2555, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(445)));
+
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_989_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(19_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2555, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(5_549_999)));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.addMSecs(4)));
+            //static assert(!__traits(compiles, ist.addMSecs(4)));
+        }
+    }
+
+    //Test roll!"usecs"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, long microseconds, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"usecs"(microseconds);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(276)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(284)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(374)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(2274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(26_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(27_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_727, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(27_001)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_766_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(766_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_766_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(767_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(272)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(264)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(174)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(998_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -33_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(967_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -33_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(966_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_833_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(167_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_833_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(166_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(276)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(284)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(374)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(1275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(2274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(26_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(27_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 26_727, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(27_001)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_766_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(766_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_766_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(767_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), 3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(272)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(264)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(174)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(999_273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(998_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -33_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(967_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -33_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(966_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_833_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(167_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_833_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(166_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)), -3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(274)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(1)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(999_999)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -2, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(999_998)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -1000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(999_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -2000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(998_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -2555, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(997_445)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -1_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -2_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(0)), -2_333_333, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"usecs"(666_667)));
+
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_989)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(19)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(19_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2555, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(25_549)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_333_333, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(3_333_329)));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"usecs"(4)));
+            //static assert(!__traits(compiles, ist.roll!"usecs"(4)));
+        }
+    }
+
+    //Test roll!"hnsecs"().
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            static void TestST(SysTime orig, long hnsecs, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.roll!"hnsecs"(hnsecs);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_998_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2555, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_997_445)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(8_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_333_333, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7_666_667)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -10_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_888_888, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_111_112)));
+
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2555, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(2554)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_333_333, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(2_333_332)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 10_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_888_888, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(888_887)));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.roll!"hnsecs"(4)));
+            //static assert(!__traits(compiles, ist.roll!"hnsecs"(4)));
+
+            //Verify Examples.
+            auto st1 = SysTime(DateTime(2010, 7, 4, 7, 32, 12));
+            st1.roll!"hnsecs"(1);
+            assert(st1 == SysTime(DateTime(2010, 7, 4, 7, 32, 12), FracSec.from!"hnsecs"(1)));
+
+            auto st2 = SysTime(DateTime(2010, 7, 4, 7, 32, 12));
+            st2.roll!"hnsecs"(-1);
+            assert(st2 == SysTime(DateTime(2010, 7, 4, 7, 32, 12), FracSec.from!"hnsecs"(9_999_999)));
+
+            auto st3 = SysTime(DateTime(2009, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+            st3.roll!"hnsecs"(1);
+            assert(st3 == SysTime(DateTime(2009, 12, 31, 23, 59, 59)));
+
+            auto st4 = SysTime(DateTime(2010, 1, 1, 0, 0, 0));
+            st4.roll!"hnsecs"(-1);
+            assert(st4 == SysTime(DateTime(2010, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)));
+
+            auto st5 = SysTime(DateTime(2009, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
+            st5.roll!"hnsecs"(1);
+            assert(st5 == SysTime(DateTime(2009, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+        }
+    }
+
+
+    /++
+        Gives the result of adding or subtracting a duration from this SysTime.
+
+        The legal types of arithmetic for SysTime using this operator are
+
+        $(TABLE
+        $(TR $(TD SysTime) $(TD +) $(TD duration) $(TD -->) $(TD SysTime))
+        $(TR $(TD SysTime) $(TD -) $(TD duration) $(TD -->) $(TD SysTime))
+        )
+
+        Params:
+            duration = The duration to add to or subtract from this SysTime.
+      +/
+    SysTime opBinary(string op, D)(in D duration) const pure nothrow
+        if((op == "+" || op == "-") &&
+           (is(Unqual!D == Duration) ||
+            is(Unqual!D == TickDuration)))
+    {
+        SysTime retval = SysTime(this._stdTime, this._timezone.get);
+
+        static if(is(Unqual!D == Duration))
+            immutable hnsecs = duration.total!"hnsecs";
+        else static if(is(Unqual!D == TickDuration))
+            immutable hnsecs = duration.hnsecs;
+
+        //Ideally, this would just be
+        //retval._stdTime += unaryFun!(op ~ "a")(hnsecs);
+        //But there isn't currently a pure version of unaryFun!().
+
+        static if(op == "+")
+            immutable signedHNSecs = hnsecs;
+        else static if(op == "-")
+            immutable signedHNSecs = -hnsecs;
+        else
+            static assert(0);
+
+        retval._stdTime += signedHNSecs;
+
+        return retval;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678));
+
+            assertPred!"=="(st + dur!"weeks"(7), SysTime(DateTime(1999, 8, 24, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"weeks"(-7), SysTime(DateTime(1999, 5, 18, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"days"(7), SysTime(DateTime(1999, 7, 13, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"days"(-7), SysTime(DateTime(1999, 6, 29, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"hours"(7), SysTime(DateTime(1999, 7, 6, 19, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"hours"(-7), SysTime(DateTime(1999, 7, 6, 5, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"minutes"(7), SysTime(DateTime(1999, 7, 6, 12, 37, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"minutes"(-7), SysTime(DateTime(1999, 7, 6, 12, 23, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"seconds"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 40), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"seconds"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 26), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st + dur!"msecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_415_678)));
+            assertPred!"=="(st + dur!"msecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_275_678)));
+            assertPred!"=="(st + dur!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_748)));
+            assertPred!"=="(st + dur!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_608)));
+            assertPred!"=="(st + dur!"hnsecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_685)));
+            assertPred!"=="(st + dur!"hnsecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_671)));
+
+            //This probably only runs in cases where gettimeofday() is used, but it's
+            //hard to do this test correctly with variable ticksPerSec.
+            if(TickDuration.ticksPerSec == 1_000_000)
+            {
+                assertPred!"=="(st + TickDuration.from!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_748)));
+                assertPred!"=="(st + TickDuration.from!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_608)));
+            }
+
+            assertPred!"=="(st - dur!"weeks"(-7), SysTime(DateTime(1999, 8, 24, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"weeks"(7), SysTime(DateTime(1999, 5, 18, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"days"(-7), SysTime(DateTime(1999, 7, 13, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"days"(7), SysTime(DateTime(1999, 6, 29, 12, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"hours"(-7), SysTime(DateTime(1999, 7, 6, 19, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"hours"(7), SysTime(DateTime(1999, 7, 6, 5, 30, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"minutes"(-7), SysTime(DateTime(1999, 7, 6, 12, 37, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"minutes"(7), SysTime(DateTime(1999, 7, 6, 12, 23, 33), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"seconds"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 40), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"seconds"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 26), FracSec.from!"hnsecs"(2_345_678)));
+            assertPred!"=="(st - dur!"msecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_415_678)));
+            assertPred!"=="(st - dur!"msecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_275_678)));
+            assertPred!"=="(st - dur!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_748)));
+            assertPred!"=="(st - dur!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_608)));
+            assertPred!"=="(st - dur!"hnsecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_685)));
+            assertPred!"=="(st - dur!"hnsecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_671)));
+
+            //This probably only runs in cases where gettimeofday() is used, but it's
+            //hard to do this test correctly with variable ticksPerSec.
+            if(TickDuration.ticksPerSec == 1_000_000)
+            {
+                assertPred!"=="(st - TickDuration.from!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_748)));
+                assertPred!"=="(st - TickDuration.from!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2_345_608)));
+            }
+
+            static void TestST(in SysTime orig, long hnsecs, in SysTime expected, size_t line = __LINE__)
+            {
+                assertPred!"=="(orig + dur!"hnsecs"(hnsecs), expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 39), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 36, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 31, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(1999, 7, 6, 13, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 27), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 24, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 29, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(1999, 7, 6, 11, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 39), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 36, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 31, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 13, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 27), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 24, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 29, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 11, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_998_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2555, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_997_445)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(8_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_333_333, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7_666_667)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -10_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 58), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_888_888, SysTime(DateTime(0, 12, 31, 23, 59, 57), FracSec.from!"hnsecs"(9_111_112)));
+
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2555, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(2554)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_333_333, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(2_333_332)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 10_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_888_888, SysTime(DateTime(1, 1, 1, 0, 0, 2), FracSec.from!"hnsecs"(888_887)));
+
+            auto duration = dur!"seconds"(12);
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst + duration));
+            //static assert(__traits(compiles, ist + duration));
+            static assert(__traits(compiles, cst - duration));
+            //static assert(__traits(compiles, ist - duration));
+        }
+    }
+
+
+    /++
+        Gives the result of adding or subtracting a duration from this SysTime,
+        as well as assigning the result to this SysTime.
+
+        The legal types of arithmetic for SysTime using this operator are
+
+        $(TABLE
+        $(TR $(TD SysTime) $(TD +) $(TD duration) $(TD -->) $(TD SysTime))
+        $(TR $(TD SysTime) $(TD -) $(TD duration) $(TD -->) $(TD SysTime))
+        )
+
+        Params:
+            duration = The duration to add to or subtract from this SysTime.
+      +/
+    /+ref+/ SysTime opOpAssign(string op, D)(in D duration) pure nothrow
+        if((op == "+" || op == "-") &&
+           (is(Unqual!D == Duration) ||
+            is(Unqual!D == TickDuration)))
+    {
+        static if(is(Unqual!D == Duration))
+            auto hnsecs = duration.total!"hnsecs";
+        else static if(is(Unqual!D == TickDuration))
+            auto hnsecs = duration.hnsecs;
+
+        //Ideally, this would just be
+        //_stdTime += unaryFun!(op ~ "a")(hnsecs);
+        //But there isn't currently a pure version of unaryFun!().
+
+        static if(op == "+")
+            immutable signedHNSecs = hnsecs;
+        else static if(op == "-")
+            immutable signedHNSecs = -hnsecs;
+        else
+            static assert(0);
+
+        _stdTime += signedHNSecs;
+
+        return this;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"weeks"(7), SysTime(DateTime(1999, 8, 24, 12, 30, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"weeks"(-7), SysTime(DateTime(1999, 5, 18, 12, 30, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"days"(7), SysTime(DateTime(1999, 7, 13, 12, 30, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"days"(-7), SysTime(DateTime(1999, 6, 29, 12, 30, 33)));
+
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hours"(7), SysTime(DateTime(1999, 7, 6, 19, 30, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hours"(-7), SysTime(DateTime(1999, 7, 6, 5, 30, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"minutes"(7), SysTime(DateTime(1999, 7, 6, 12, 37, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"minutes"(-7), SysTime(DateTime(1999, 7, 6, 12, 23, 33)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"seconds"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 40)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"seconds"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 26)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"msecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(7)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"msecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(993)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"usecs"(999_993)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hnsecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(7)));
+            assertPred!"+="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hnsecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_993)));
+
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"weeks"(-7), SysTime(DateTime(1999, 8, 24, 12, 30, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"weeks"(7), SysTime(DateTime(1999, 5, 18, 12, 30, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"days"(-7), SysTime(DateTime(1999, 7, 13, 12, 30, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"days"(7), SysTime(DateTime(1999, 6, 29, 12, 30, 33)));
+
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hours"(-7), SysTime(DateTime(1999, 7, 6, 19, 30, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hours"(7), SysTime(DateTime(1999, 7, 6, 5, 30, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"minutes"(-7), SysTime(DateTime(1999, 7, 6, 12, 37, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"minutes"(7), SysTime(DateTime(1999, 7, 6, 12, 23, 33)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"seconds"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 40)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"seconds"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 26)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"msecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(7)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"msecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"msecs"(993)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"usecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(7)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"usecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"usecs"(999_993)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hnsecs"(-7), SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(7)));
+            assertPred!"-="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)), dur!"hnsecs"(7), SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_993)));
+
+            static void TestST(SysTime orig, long hnsecs, in SysTime expected, size_t line = __LINE__)
+            {
+                orig += dur!"hnsecs"(hnsecs);
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 39), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 36, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 31, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(1999, 7, 6, 13, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(1999, 7, 6, 12, 30, 27), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 24, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(1999, 7, 6, 12, 29, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(1999, 7, 6, 11, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test B.C.
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 0, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(276)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(284)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(374)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1275)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(2274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(26_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 26_727, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(27_001)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_725, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_766_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_766_726, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_767_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 39), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 36, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 31, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), 36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 13, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(272)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -10, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(264)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -100, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(174)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -274, SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1001, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_999_273)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -2000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_998_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_967_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -33_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_966_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_274, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_167_000)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_833_275, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(8_166_999)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -1_000_000, SysTime(DateTime(-1999, 7, 6, 12, 30, 32), FracSec.from!"hnsecs"(9_000_274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -60_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 30, 27), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -3_600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 24, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -600_000_000L, SysTime(DateTime(-1999, 7, 6, 12, 29, 33), FracSec.from!"hnsecs"(274)));
+            TestST(SysTime(DateTime(-1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(274)), -36_000_000_000L, SysTime(DateTime(-1999, 7, 6, 11, 30, 33), FracSec.from!"hnsecs"(274)));
+
+            //Test Both
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_998_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2555, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_997_445)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -1_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(8_000_000)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -2_333_333, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7_666_667)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -10_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_000_000, SysTime(DateTime(0, 12, 31, 23, 59, 58), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), -20_888_888, SysTime(DateTime(0, 12, 31, 23, 59, 57), FracSec.from!"hnsecs"(9_111_112)));
+
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), -1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2555, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(2554)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 2_333_333, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(2_333_332)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 10_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_000_000, SysTime(DateTime(1, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(9_999_999)));
+            TestST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 20_888_888, SysTime(DateTime(1, 1, 1, 0, 0, 2), FracSec.from!"hnsecs"(888_887)));
+
+            auto duration = dur!"seconds"(12);
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst += duration));
+            //static assert(!__traits(compiles, ist += duration));
+            static assert(!__traits(compiles, cst -= duration));
+            //static assert(!__traits(compiles, ist -= duration));
+        }
+    }
+
+
+    /++
+        Gives the difference between two SysTimes.
+
+        The legal types of arithmetic for SysTime using this operator are
+
+        $(TABLE
+        $(TR $(TD SysTime) $(TD -) $(TD SysTime) $(TD -->) $(TD duration))
+        )
+      +/
+    Duration opBinary(string op)(in SysTime rhs) const pure nothrow
+        if(op == "-")
+    {
+        return dur!"hnsecs"(_stdTime - rhs._stdTime);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1998, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(31_536_000));
+            assertPred!"=="(SysTime(DateTime(1998, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(-31_536_000));
+
+            assertPred!"=="(SysTime(DateTime(1999, 8, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(26_78_400));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 8, 6, 12, 30, 33)),
+                        dur!"seconds"(-26_78_400));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 5, 12, 30, 33)),
+                        dur!"seconds"(86_400));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 5, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(-86_400));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 11, 30, 33)),
+                        dur!"seconds"(3600));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 11, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(-3600));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 31, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(60));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 31, 33)),
+                        dur!"seconds"(-60));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 34)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"seconds"(1));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 34)),
+                        dur!"seconds"(-1));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(532)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"msecs"(532));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"msecs"(532)),
+                        dur!"msecs"(-532));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(333_347)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"usecs"(333_347));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"usecs"(333_347)),
+                        dur!"usecs"(-333_347));
+
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_234_567)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33)),
+                        dur!"hnsecs"(1_234_567));
+            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)) - SysTime(DateTime(1999, 7, 6, 12, 30, 33), FracSec.from!"hnsecs"(1_234_567)),
+                        dur!"hnsecs"(-1_234_567));
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 30, 33)) - SysTime(DateTime(1, 1, 1, 0, 0, 0)), dur!"seconds"(45033));
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0)) - SysTime(DateTime(1, 1, 1, 12, 30, 33)), dur!"seconds"(-45033));
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 30, 33)) - SysTime(DateTime(1, 1, 1, 0, 0, 0)), dur!"seconds"(-41367));
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0)) - SysTime(DateTime(0, 12, 31, 12, 30, 33)), dur!"seconds"(41367));
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0)) - SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)),
+                            dur!"hnsecs"(1));
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)) - SysTime(DateTime(1, 1, 1, 0, 0, 0)),
+                            dur!"hnsecs"(-1));
+
+            auto tz = TimeZone.getTimeZone("America/Los_Angeles");
+
+            assertPred!"=="(SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), tz) -
+                            SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), tz),
+                            dur!"hnsecs"(0));
+
+            assertPred!"=="(SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), tz) -
+                            SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), UTC()),
+                            dur!"hours"(8));
+
+            assertPred!"=="(SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), UTC()) -
+                            SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), tz),
+                            dur!"hours"(-8));
+
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st - st));
+            static assert(__traits(compiles, cst - st));
+            //static assert(__traits(compiles, ist - st));
+
+            static assert(__traits(compiles, st - cst));
+            static assert(__traits(compiles, cst - cst));
+            //static assert(__traits(compiles, ist - cst));
+
+            //static assert(__traits(compiles, st - ist));
+            //static assert(__traits(compiles, cst - ist));
+            //static assert(__traits(compiles, ist - ist));
+        }
+    }
+
+
+    /++
+        Returns the difference between the two SysTimes in months.
+
+        You can get the difference in years by subtracting the year property
+        of two SysTimes, and you can get the difference in days or weeks by
+        subtracting the SysTimes themselves and using the Duration that results,
+        but because you cannot convert between months and smaller units without
+        a specific date (which the Duration from the subtraction of two SysTimes
+        won't have), you cannot get the difference in months without doing some
+        math using both the year and month properties, so this is a convenience
+        function for getting the difference in months.
+
+        Note that the number of days in the months or how far into the month either
+        date is is irrelevant. It is the difference in the month property combined
+        with the difference in years * 12. So, for instance, December 31st and
+        January 1st are one month apart just as December 1st and January 31st are
+        one month apart.
+
+        Params:
+            rhs = The SysTime to subtract from this one.
+
+        Examples:
+--------------------
+assert(SysTime(Date(1999, 2, 1)).diffMonths(SysTime(Date(1999, 1, 31))) == 1);
+assert(SysTime(Date(1999, 1, 31)).diffMonths(SysTime(Date(1999, 2, 1))) == -1);
+assert(SysTime(Date(1999, 3, 1)).diffMonths(SysTime(Date(1999, 1, 1))) == 2);
+assert(SysTime(Date(1999, 1, 1)).diffMonths(SysTime(Date(1999, 3, 31))) == -2);
+--------------------
+      +/
+    int diffMonths(in SysTime rhs) const nothrow
+    {
+        return (cast(Date)this).diffMonths(cast(Date)rhs);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.diffMonths(st)));
+            static assert(__traits(compiles, cst.diffMonths(st)));
+            //static assert(__traits(compiles, ist.diffMonths(st)));
+
+            static assert(__traits(compiles, st.diffMonths(cst)));
+            static assert(__traits(compiles, cst.diffMonths(cst)));
+            //static assert(__traits(compiles, ist.diffMonths(cst)));
+
+            //static assert(__traits(compiles, st.diffMonths(ist)));
+            //static assert(__traits(compiles, cst.diffMonths(ist)));
+            //static assert(__traits(compiles, ist.diffMonths(ist)));
+
+            //Verify Examples.
+            assert(SysTime(Date(1999, 2, 1)).diffMonths(SysTime(Date(1999, 1, 31))) == 1);
+            assert(SysTime(Date(1999, 1, 31)).diffMonths(SysTime(Date(1999, 2, 1))) == -1);
+            assert(SysTime(Date(1999, 3, 1)).diffMonths(SysTime(Date(1999, 1, 1))) == 2);
+            assert(SysTime(Date(1999, 1, 1)).diffMonths(SysTime(Date(1999, 3, 31))) == -2);
+        }
+    }
+
+
+    /++
+        Whether this SysTime is in a leap year.
+     +/
+    @property bool isLeapYear() const nothrow
+    {
+        return (cast(Date)this).isLeapYear;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.isLeapYear));
+            static assert(__traits(compiles, cst.isLeapYear));
+            //static assert(__traits(compiles, ist.isLeapYear));
+        }
+    }
+
+
+    /++
+        Day of the week this SysTime is on.
+      +/
+    @property DayOfWeek dayOfWeek() const nothrow
+    {
+        return getDayOfWeek(dayOfGregorianCal);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.dayOfWeek));
+            static assert(__traits(compiles, cst.dayOfWeek));
+            //static assert(__traits(compiles, ist.dayOfWeek));
+        }
+    }
+
+
+    /++
+        Day of the year this SysTime is on.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 1, 1, 12, 22, 7)).dayOfYear == 1);
+assert(SysTime(DateTime(1999, 12, 31, 7, 2, 59)).dayOfYear == 365);
+assert(SysTime(DateTime(2000, 12, 31, 21, 20, 0)).dayOfYear == 366);
+--------------------
+      +/
+    @property ushort dayOfYear() const nothrow
+    {
+        return (cast(Date)this).dayOfYear;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.dayOfYear));
+            static assert(__traits(compiles, cst.dayOfYear));
+            //static assert(__traits(compiles, ist.dayOfYear));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 1, 1, 12, 22, 7)).dayOfYear == 1);
+            assert(SysTime(DateTime(1999, 12, 31, 7, 2, 59)).dayOfYear == 365);
+            assert(SysTime(DateTime(2000, 12, 31, 21, 20, 0)).dayOfYear == 366);
+        }
+    }
+
+
+    /++
+        Day of the year.
+
+        Params:
+            day = The day of the year to set which day of the year this SysTime is on.
+      +/
+    @property void dayOfYear(int day)
+    {
+        immutable hnsecs = adjTime;
+        immutable days = convert!("hnsecs", "days")(hnsecs);
+        immutable theRest = hnsecs - convert!("days", "hnsecs")(days);
+
+        auto date = Date(cast(int)days);
+        date.dayOfYear = day;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
+
+        adjTime = newDaysHNSecs + theRest;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.dayOfYear = 12));
+            static assert(!__traits(compiles, cst.dayOfYear = 12));
+            //static assert(!__traits(compiles, ist.dayOfYear = 12));
+        }
+    }
+
+
+    /++
+        The Xth day of the Gregorian Calendar that this SysTime is on.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1, 1, 1, 0, 0, 0)).dayOfGregorianCal == 1);
+assert(SysTime(DateTime(1, 12, 31, 23, 59, 59)).dayOfGregorianCal == 365);
+assert(SysTime(DateTime(2, 1, 1, 2, 2, 2)).dayOfGregorianCal == 366);
+
+assert(SysTime(DateTime(0, 12, 31, 7, 7, 7)).dayOfGregorianCal == 0);
+assert(SysTime(DateTime(0, 1, 1, 19, 30, 0)).dayOfGregorianCal == -365);
+assert(SysTime(DateTime(-1, 12, 31, 4, 7, 0)).dayOfGregorianCal == -366);
+
+assert(SysTime(DateTime(2000, 1, 1, 9, 30, 20)).dayOfGregorianCal == 730_120);
+assert(SysTime(DateTime(2010, 12, 31, 15, 45, 50)).dayOfGregorianCal == 734_137);
+--------------------
+     +/
+    @property int dayOfGregorianCal() const nothrow
+    {
+        immutable adjustedTime = adjTime;
+
+        //We have to add one because 0 would be midnight, January 1st, 1 A.D., which would be
+        //the 1st day of the Gregorian Calendar, not the 0th. So, simply casting to days
+        //is one day off.
+        if(adjustedTime > 0)
+            return cast(int)getUnitsFromHNSecs!"days"(adjustedTime) + 1;
+
+        auto hnsecs = adjustedTime;
+        immutable days = cast(int)splitUnitsFromHNSecs!"days"(hnsecs);
+
+        return hnsecs == 0 ? days + 1 : days;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal, 1);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)).dayOfGregorianCal, 1);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal, 1);
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 1);
+            assertPred!"=="(SysTime(DateTime(1, 1, 2, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 2);
+            assertPred!"=="(SysTime(DateTime(1, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 32);
+            assertPred!"=="(SysTime(DateTime(2, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 366);
+            assertPred!"=="(SysTime(DateTime(3, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 731);
+            assertPred!"=="(SysTime(DateTime(4, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 1096);
+            assertPred!"=="(SysTime(DateTime(5, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 1462);
+            assertPred!"=="(SysTime(DateTime(50, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 17_898);
+            assertPred!"=="(SysTime(DateTime(97, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 35_065);
+            assertPred!"=="(SysTime(DateTime(100, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 36_160);
+            assertPred!"=="(SysTime(DateTime(101, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 36_525);
+            assertPred!"=="(SysTime(DateTime(105, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 37_986);
+            assertPred!"=="(SysTime(DateTime(200, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 72_684);
+            assertPred!"=="(SysTime(DateTime(201, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 73_049);
+            assertPred!"=="(SysTime(DateTime(300, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 109_208);
+            assertPred!"=="(SysTime(DateTime(301, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 109_573);
+            assertPred!"=="(SysTime(DateTime(400, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 145_732);
+            assertPred!"=="(SysTime(DateTime(401, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 146_098);
+            assertPred!"=="(SysTime(DateTime(500, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 182_257);
+            assertPred!"=="(SysTime(DateTime(501, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 182_622);
+            assertPred!"=="(SysTime(DateTime(1000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 364_878);
+            assertPred!"=="(SysTime(DateTime(1001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 365_243);
+            assertPred!"=="(SysTime(DateTime(1600, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 584_023);
+            assertPred!"=="(SysTime(DateTime(1601, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 584_389);
+            assertPred!"=="(SysTime(DateTime(1900, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 693_596);
+            assertPred!"=="(SysTime(DateTime(1901, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 693_961);
+            assertPred!"=="(SysTime(DateTime(1945, 11, 12, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 710_347);
+            assertPred!"=="(SysTime(DateTime(1999, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 729_755);
+            assertPred!"=="(SysTime(DateTime(2000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 730_120);
+            assertPred!"=="(SysTime(DateTime(2001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 730_486);
+
+            assertPred!"=="(SysTime(DateTime(2010, 1, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_773);
+            assertPred!"=="(SysTime(DateTime(2010, 1, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_803);
+            assertPred!"=="(SysTime(DateTime(2010, 2, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_804);
+            assertPred!"=="(SysTime(DateTime(2010, 2, 28, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_831);
+            assertPred!"=="(SysTime(DateTime(2010, 3, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_832);
+            assertPred!"=="(SysTime(DateTime(2010, 3, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_862);
+            assertPred!"=="(SysTime(DateTime(2010, 4, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_863);
+            assertPred!"=="(SysTime(DateTime(2010, 4, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_892);
+            assertPred!"=="(SysTime(DateTime(2010, 5, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_893);
+            assertPred!"=="(SysTime(DateTime(2010, 5, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_923);
+            assertPred!"=="(SysTime(DateTime(2010, 6, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_924);
+            assertPred!"=="(SysTime(DateTime(2010, 6, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_953);
+            assertPred!"=="(SysTime(DateTime(2010, 7, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_954);
+            assertPred!"=="(SysTime(DateTime(2010, 7, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_984);
+            assertPred!"=="(SysTime(DateTime(2010, 8, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 733_985);
+            assertPred!"=="(SysTime(DateTime(2010, 8, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_015);
+            assertPred!"=="(SysTime(DateTime(2010, 9, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_016);
+            assertPred!"=="(SysTime(DateTime(2010, 9, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_045);
+            assertPred!"=="(SysTime(DateTime(2010, 10, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_046);
+            assertPred!"=="(SysTime(DateTime(2010, 10, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_076);
+            assertPred!"=="(SysTime(DateTime(2010, 11, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_077);
+            assertPred!"=="(SysTime(DateTime(2010, 11, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_106);
+            assertPred!"=="(SysTime(DateTime(2010, 12, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_107);
+            assertPred!"=="(SysTime(DateTime(2010, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, 734_137);
+
+            assertPred!"=="(SysTime(DateTime(2012, 2, 1, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, 734_534);
+            assertPred!"=="(SysTime(DateTime(2012, 2, 28, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, 734_561);
+            assertPred!"=="(SysTime(DateTime(2012, 2, 29, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, 734_562);
+            assertPred!"=="(SysTime(DateTime(2012, 3, 1, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, 734_563);
+
+            //Test B.C.
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal, 0);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)).dayOfGregorianCal, 0);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal, 0);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(1)).dayOfGregorianCal, 0);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal, 0);
+
+            assertPred!"=="(SysTime(DateTime(-1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal, -366);
+            assertPred!"=="(SysTime(DateTime(-1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_998)).dayOfGregorianCal, -366);
+            assertPred!"=="(SysTime(DateTime(-1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal, -366);
+            assertPred!"=="(SysTime(DateTime(-1, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal, -366);
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, 0);
+            assertPred!"=="(SysTime(DateTime(0, 12, 30, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1);
+            assertPred!"=="(SysTime(DateTime(0, 12, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -30);
+            assertPred!"=="(SysTime(DateTime(0, 11, 30, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -31);
+
+            assertPred!"=="(SysTime(DateTime(-1, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -366);
+            assertPred!"=="(SysTime(DateTime(-1, 12, 30, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -367);
+            assertPred!"=="(SysTime(DateTime(-1, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -730);
+            assertPred!"=="(SysTime(DateTime(-2, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -731);
+            assertPred!"=="(SysTime(DateTime(-2, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1095);
+            assertPred!"=="(SysTime(DateTime(-3, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1096);
+            assertPred!"=="(SysTime(DateTime(-3, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1460);
+            assertPred!"=="(SysTime(DateTime(-4, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1461);
+            assertPred!"=="(SysTime(DateTime(-4, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1826);
+            assertPred!"=="(SysTime(DateTime(-5, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -1827);
+            assertPred!"=="(SysTime(DateTime(-5, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -2191);
+            assertPred!"=="(SysTime(DateTime(-9, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -3652);
+
+            assertPred!"=="(SysTime(DateTime(-49, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -18_262);
+            assertPred!"=="(SysTime(DateTime(-50, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -18_627);
+            assertPred!"=="(SysTime(DateTime(-97, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -35_794);
+            assertPred!"=="(SysTime(DateTime(-99, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -36_160);
+            assertPred!"=="(SysTime(DateTime(-99, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -36_524);
+            assertPred!"=="(SysTime(DateTime(-100, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -36_889);
+            assertPred!"=="(SysTime(DateTime(-101, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -37_254);
+            assertPred!"=="(SysTime(DateTime(-105, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -38_715);
+            assertPred!"=="(SysTime(DateTime(-200, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -73_413);
+            assertPred!"=="(SysTime(DateTime(-201, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -73_778);
+            assertPred!"=="(SysTime(DateTime(-300, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -109_937);
+            assertPred!"=="(SysTime(DateTime(-301, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -110_302);
+            assertPred!"=="(SysTime(DateTime(-400, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -146_097);
+            assertPred!"=="(SysTime(DateTime(-400, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -146_462);
+            assertPred!"=="(SysTime(DateTime(-401, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -146_827);
+            assertPred!"=="(SysTime(DateTime(-499, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -182_621);
+            assertPred!"=="(SysTime(DateTime(-500, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -182_986);
+            assertPred!"=="(SysTime(DateTime(-501, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -183_351);
+            assertPred!"=="(SysTime(DateTime(-1000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -365_607);
+            assertPred!"=="(SysTime(DateTime(-1001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -365_972);
+            assertPred!"=="(SysTime(DateTime(-1599, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -584_387);
+            assertPred!"=="(SysTime(DateTime(-1600, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -584_388);
+            assertPred!"=="(SysTime(DateTime(-1600, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -584_753);
+            assertPred!"=="(SysTime(DateTime(-1601, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -585_118);
+            assertPred!"=="(SysTime(DateTime(-1900, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -694_325);
+            assertPred!"=="(SysTime(DateTime(-1901, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -694_690);
+            assertPred!"=="(SysTime(DateTime(-1999, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -730_484);
+            assertPred!"=="(SysTime(DateTime(-2000, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -730_485);
+            assertPred!"=="(SysTime(DateTime(-2000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -730_850);
+            assertPred!"=="(SysTime(DateTime(-2001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)).dayOfGregorianCal, -731_215);
+
+            assertPred!"=="(SysTime(DateTime(-2010, 1, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_502);
+            assertPred!"=="(SysTime(DateTime(-2010, 1, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_472);
+            assertPred!"=="(SysTime(DateTime(-2010, 2, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_471);
+            assertPred!"=="(SysTime(DateTime(-2010, 2, 28, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_444);
+            assertPred!"=="(SysTime(DateTime(-2010, 3, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_443);
+            assertPred!"=="(SysTime(DateTime(-2010, 3, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_413);
+            assertPred!"=="(SysTime(DateTime(-2010, 4, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_412);
+            assertPred!"=="(SysTime(DateTime(-2010, 4, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_383);
+            assertPred!"=="(SysTime(DateTime(-2010, 5, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_382);
+            assertPred!"=="(SysTime(DateTime(-2010, 5, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_352);
+            assertPred!"=="(SysTime(DateTime(-2010, 6, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_351);
+            assertPred!"=="(SysTime(DateTime(-2010, 6, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_322);
+            assertPred!"=="(SysTime(DateTime(-2010, 7, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_321);
+            assertPred!"=="(SysTime(DateTime(-2010, 7, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_291);
+            assertPred!"=="(SysTime(DateTime(-2010, 8, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_290);
+            assertPred!"=="(SysTime(DateTime(-2010, 8, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_260);
+            assertPred!"=="(SysTime(DateTime(-2010, 9, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_259);
+            assertPred!"=="(SysTime(DateTime(-2010, 9, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_230);
+            assertPred!"=="(SysTime(DateTime(-2010, 10, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_229);
+            assertPred!"=="(SysTime(DateTime(-2010, 10, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_199);
+            assertPred!"=="(SysTime(DateTime(-2010, 11, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_198);
+            assertPred!"=="(SysTime(DateTime(-2010, 11, 30, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_169);
+            assertPred!"=="(SysTime(DateTime(-2010, 12, 1, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_168);
+            assertPred!"=="(SysTime(DateTime(-2010, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999)).dayOfGregorianCal, -734_138);
+
+            assertPred!"=="(SysTime(DateTime(-2012, 2, 1, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, -735_202);
+            assertPred!"=="(SysTime(DateTime(-2012, 2, 28, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, -735_175);
+            assertPred!"=="(SysTime(DateTime(-2012, 2, 29, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, -735_174);
+            assertPred!"=="(SysTime(DateTime(-2012, 3, 1, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, -735_173);
+
+            assertPred!"=="(SysTime(DateTime(-3760, 9, 7, 0, 0, 0), FracSec.from!"msecs"(0)).dayOfGregorianCal, -1_373_427); //Start of Hebrew Calendar
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.dayOfGregorianCal));
+            //static assert(__traits(compiles, ist.dayOfGregorianCal));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1, 1, 1, 0, 0, 0)).dayOfGregorianCal == 1);
+            assert(SysTime(DateTime(1, 12, 31, 23, 59, 59)).dayOfGregorianCal == 365);
+            assert(SysTime(DateTime(2, 1, 1, 2, 2, 2)).dayOfGregorianCal == 366);
+
+            assert(SysTime(DateTime(0, 12, 31, 7, 7, 7)).dayOfGregorianCal == 0);
+            assert(SysTime(DateTime(0, 1, 1, 19, 30, 0)).dayOfGregorianCal == -365);
+            assert(SysTime(DateTime(-1, 12, 31, 4, 7, 0)).dayOfGregorianCal == -366);
+
+            assert(SysTime(DateTime(2000, 1, 1, 9, 30, 20)).dayOfGregorianCal == 730_120);
+            assert(SysTime(DateTime(2010, 12, 31, 15, 45, 50)).dayOfGregorianCal == 734_137);
+        }
+    }
+
+
+    //Test that the logic for the day of the Gregorian Calendar is consistent
+    //between Date and SysTime.
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(Date(1, 1, 1).dayOfGregorianCal, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(1, 1, 2).dayOfGregorianCal, SysTime(DateTime(1, 1, 2, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(1, 2, 1).dayOfGregorianCal, SysTime(DateTime(1, 2, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2, 1, 1).dayOfGregorianCal, SysTime(DateTime(2, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(3, 1, 1).dayOfGregorianCal, SysTime(DateTime(3, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(4, 1, 1).dayOfGregorianCal, SysTime(DateTime(4, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(5, 1, 1).dayOfGregorianCal, SysTime(DateTime(5, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(50, 1, 1).dayOfGregorianCal, SysTime(DateTime(50, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(97, 1, 1).dayOfGregorianCal, SysTime(DateTime(97, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(100, 1, 1).dayOfGregorianCal, SysTime(DateTime(100, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(101, 1, 1).dayOfGregorianCal, SysTime(DateTime(101, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(105, 1, 1).dayOfGregorianCal, SysTime(DateTime(105, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(200, 1, 1).dayOfGregorianCal, SysTime(DateTime(200, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(201, 1, 1).dayOfGregorianCal, SysTime(DateTime(201, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(300, 1, 1).dayOfGregorianCal, SysTime(DateTime(300, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(301, 1, 1).dayOfGregorianCal, SysTime(DateTime(301, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(400, 1, 1).dayOfGregorianCal, SysTime(DateTime(400, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(401, 1, 1).dayOfGregorianCal, SysTime(DateTime(401, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(500, 1, 1).dayOfGregorianCal, SysTime(DateTime(500, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(501, 1, 1).dayOfGregorianCal, SysTime(DateTime(501, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(1000, 1, 1).dayOfGregorianCal, SysTime(DateTime(1000, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(1001, 1, 1).dayOfGregorianCal, SysTime(DateTime(1001, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(1600, 1, 1).dayOfGregorianCal, SysTime(DateTime(1600, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(1601, 1, 1).dayOfGregorianCal, SysTime(DateTime(1601, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(1900, 1, 1).dayOfGregorianCal, SysTime(DateTime(1900, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(1901, 1, 1).dayOfGregorianCal, SysTime(DateTime(1901, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(1945, 11, 12).dayOfGregorianCal, SysTime(DateTime(1945, 11, 12, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(1999, 1, 1).dayOfGregorianCal, SysTime(DateTime(1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(1999, 7, 6).dayOfGregorianCal, SysTime(DateTime(1999, 7, 6, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2000, 1, 1).dayOfGregorianCal, SysTime(DateTime(2000, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2001, 1, 1).dayOfGregorianCal, SysTime(DateTime(2001, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(2010, 1, 1).dayOfGregorianCal, SysTime(DateTime(2010, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 1, 31).dayOfGregorianCal, SysTime(DateTime(2010, 1, 31, 23, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 2, 1).dayOfGregorianCal, SysTime(DateTime(2010, 2, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 2, 28).dayOfGregorianCal, SysTime(DateTime(2010, 2, 28, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 3, 1).dayOfGregorianCal, SysTime(DateTime(2010, 3, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 3, 31).dayOfGregorianCal, SysTime(DateTime(2010, 3, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 4, 1).dayOfGregorianCal, SysTime(DateTime(2010, 4, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 4, 30).dayOfGregorianCal, SysTime(DateTime(2010, 4, 30, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 5, 1).dayOfGregorianCal, SysTime(DateTime(2010, 5, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 5, 31).dayOfGregorianCal, SysTime(DateTime(2010, 5, 31, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 6, 1).dayOfGregorianCal, SysTime(DateTime(2010, 6, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 6, 30).dayOfGregorianCal, SysTime(DateTime(2010, 6, 30, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 7, 1).dayOfGregorianCal, SysTime(DateTime(2010, 7, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 7, 31).dayOfGregorianCal, SysTime(DateTime(2010, 7, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 8, 1).dayOfGregorianCal, SysTime(DateTime(2010, 8, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 8, 31).dayOfGregorianCal, SysTime(DateTime(2010, 8, 31, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 9, 1).dayOfGregorianCal, SysTime(DateTime(2010, 9, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 9, 30).dayOfGregorianCal, SysTime(DateTime(2010, 9, 30, 12, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 10, 1).dayOfGregorianCal, SysTime(DateTime(2010, 10, 1, 0, 12, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 10, 31).dayOfGregorianCal, SysTime(DateTime(2010, 10, 31, 0, 0, 12), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 11, 1).dayOfGregorianCal, SysTime(DateTime(2010, 11, 1, 23, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 11, 30).dayOfGregorianCal, SysTime(DateTime(2010, 11, 30, 0, 59, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 12, 1).dayOfGregorianCal, SysTime(DateTime(2010, 12, 1, 0, 0, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(2010, 12, 31).dayOfGregorianCal, SysTime(DateTime(2010, 12, 31, 0, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(2012, 2, 1).dayOfGregorianCal, SysTime(DateTime(2012, 2, 1, 23, 0, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(2012, 2, 28).dayOfGregorianCal, SysTime(DateTime(2012, 2, 28, 23, 59, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(2012, 2, 29).dayOfGregorianCal, SysTime(DateTime(2012, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(7)).dayOfGregorianCal);
+            assertPred!"=="(Date(2012, 3, 1).dayOfGregorianCal, SysTime(DateTime(2012, 3, 1, 7, 7, 7), FracSec.from!"hnsecs"(7)).dayOfGregorianCal);
+
+            //Test B.C.
+            assertPred!"=="(Date(0, 12, 31).dayOfGregorianCal, SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(0, 12, 30).dayOfGregorianCal, SysTime(DateTime(0, 12, 30, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(0, 12, 1).dayOfGregorianCal, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(0, 11, 30).dayOfGregorianCal, SysTime(DateTime(0, 11, 30, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(-1, 12, 31).dayOfGregorianCal, SysTime(DateTime(-1, 12, 31, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1, 12, 30).dayOfGregorianCal, SysTime(DateTime(-1, 12, 30, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2, 12, 31).dayOfGregorianCal, SysTime(DateTime(-2, 12, 31, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2, 1, 1).dayOfGregorianCal, SysTime(DateTime(-2, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-3, 12, 31).dayOfGregorianCal, SysTime(DateTime(-3, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-3, 1, 1).dayOfGregorianCal, SysTime(DateTime(-3, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-4, 12, 31).dayOfGregorianCal, SysTime(DateTime(-4, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-4, 1, 1).dayOfGregorianCal, SysTime(DateTime(-4, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-5, 12, 31).dayOfGregorianCal, SysTime(DateTime(-5, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-5, 1, 1).dayOfGregorianCal, SysTime(DateTime(-5, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-9, 1, 1).dayOfGregorianCal, SysTime(DateTime(-9, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(-49, 1, 1).dayOfGregorianCal, SysTime(DateTime(-49, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-50, 1, 1).dayOfGregorianCal, SysTime(DateTime(-50, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-97, 1, 1).dayOfGregorianCal, SysTime(DateTime(-97, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-99, 12, 31).dayOfGregorianCal, SysTime(DateTime(-99, 12, 31, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-99, 1, 1).dayOfGregorianCal, SysTime(DateTime(-99, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-100, 1, 1).dayOfGregorianCal, SysTime(DateTime(-100, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-101, 1, 1).dayOfGregorianCal, SysTime(DateTime(-101, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-105, 1, 1).dayOfGregorianCal, SysTime(DateTime(-105, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-200, 1, 1).dayOfGregorianCal, SysTime(DateTime(-200, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-201, 1, 1).dayOfGregorianCal, SysTime(DateTime(-201, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-300, 1, 1).dayOfGregorianCal, SysTime(DateTime(-300, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-301, 1, 1).dayOfGregorianCal, SysTime(DateTime(-301, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-400, 12, 31).dayOfGregorianCal, SysTime(DateTime(-400, 12, 31, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-400, 1, 1).dayOfGregorianCal, SysTime(DateTime(-400, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-401, 1, 1).dayOfGregorianCal, SysTime(DateTime(-401, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-499, 1, 1).dayOfGregorianCal, SysTime(DateTime(-499, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-500, 1, 1).dayOfGregorianCal, SysTime(DateTime(-500, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-501, 1, 1).dayOfGregorianCal, SysTime(DateTime(-501, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1000, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1000, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1001, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1001, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1599, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1599, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1600, 12, 31).dayOfGregorianCal, SysTime(DateTime(-1600, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1600, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1600, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1601, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1601, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1900, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1900, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1901, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1901, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1999, 1, 1).dayOfGregorianCal, SysTime(DateTime(-1999, 1, 1, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-1999, 7, 6).dayOfGregorianCal, SysTime(DateTime(-1999, 7, 6, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2000, 12, 31).dayOfGregorianCal, SysTime(DateTime(-2000, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2000, 1, 1).dayOfGregorianCal, SysTime(DateTime(-2000, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2001, 1, 1).dayOfGregorianCal, SysTime(DateTime(-2001, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(-2010, 1, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 1, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 1, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 2, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 2, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 2, 28).dayOfGregorianCal, SysTime(DateTime(-2010, 2, 28, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 3, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 3, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 3, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 3, 31, 12, 13, 14), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 4, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 4, 1, 12, 13, 14), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 4, 30).dayOfGregorianCal, SysTime(DateTime(-2010, 4, 30, 12, 13, 14), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 5, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 5, 1, 12, 13, 14), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 5, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 5, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 6, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 6, 1, 23, 59, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 6, 30).dayOfGregorianCal, SysTime(DateTime(-2010, 6, 30, 23, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 7, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 7, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 7, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 7, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 8, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 8, 1, 0, 0, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 8, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 8, 31, 0, 0, 0), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 9, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 9, 1, 0, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 9, 30).dayOfGregorianCal, SysTime(DateTime(-2010, 9, 30, 12, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 10, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 10, 1, 0, 12, 0), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 10, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 10, 31, 0, 0, 12), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 11, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 11, 1, 23, 0, 0), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 11, 30).dayOfGregorianCal, SysTime(DateTime(-2010, 11, 30, 0, 59, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 12, 1).dayOfGregorianCal, SysTime(DateTime(-2010, 12, 1, 0, 0, 59), FracSec.from!"hnsecs"(500)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2010, 12, 31).dayOfGregorianCal, SysTime(DateTime(-2010, 12, 31, 0, 59, 59), FracSec.from!"hnsecs"(50_000)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(-2012, 2, 1).dayOfGregorianCal, SysTime(DateTime(-2012, 2, 1, 23, 0, 59), FracSec.from!"hnsecs"(9_999_999)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2012, 2, 28).dayOfGregorianCal, SysTime(DateTime(-2012, 2, 28, 23, 59, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2012, 2, 29).dayOfGregorianCal, SysTime(DateTime(-2012, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(7)).dayOfGregorianCal);
+            assertPred!"=="(Date(-2012, 3, 1).dayOfGregorianCal, SysTime(DateTime(-2012, 3, 1, 7, 7, 7), FracSec.from!"hnsecs"(7)).dayOfGregorianCal);
+
+            assertPred!"=="(Date(-3760, 9, 7).dayOfGregorianCal, SysTime(DateTime(-3760, 9, 7, 0, 0, 0), FracSec.from!"hnsecs"(0)).dayOfGregorianCal);
+        }
+    }
+
+
+    /++
+        The Xth day of the Gregorian Calendar that this SysTime is on. Setting
+        this property does not affect the time portion of SysTime.
+
+        Params:
+            days = The day of the Gregorian Calendar to set this Date to.
+
+        Examples:
+--------------------
+auto st = SysTime(DateTime(0, 0, 0, 12, 0, 0));
+st.dayOfGregorianCal = 1;
+assert(st == SysTime(DateTime(1, 1, 1, 12, 0, 0)));
+
+st.dayOfGregorianCal = 365;
+assert(st == SysTime(DateTime(1, 12, 31, 12, 0, 0)));
+
+st.dayOfGregorianCal = 366;
+assert(st == SysTime(DateTime(2, 1, 1, 12, 0, 0)));
+
+st.dayOfGregorianCal = 0;
+assert(st == SysTime(DateTime(0, 12, 31, 12, 0, 0)));
+
+st.dayOfGregorianCal = -365;
+assert(st == SysTime(DateTime(-0, 1, 1, 12, 0, 0)));
+
+st.dayOfGregorianCal = -366;
+assert(st == SysTime(DateTime(-1, 12, 31, 12, 0, 0)));
+
+st.dayOfGregorianCal = 730_120;
+assert(st == SysTime(DateTime(2000, 1, 1, 12, 0, 0)));
+
+st.dayOfGregorianCal = 734_137;
+assert(st == SysTime(DateTime(2010, 12, 31, 12, 0, 0)));
+--------------------
+     +/
+    @property void dayOfGregorianCal(int days) nothrow
+    {
+        auto hnsecs = adjTime;
+        hnsecs = removeUnitsFromHNSecs!"days"(hnsecs);
+
+        if(hnsecs < 0)
+            hnsecs += convert!("hours", "hnsecs")(24);
+
+        if(--days < 0)
+        {
+            hnsecs -= convert!("hours", "hnsecs")(24);
+            ++days;
+        }
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
+
+        adjTime = newDaysHNSecs + hnsecs;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            void testST(SysTime orig, int day, in SysTime expected, size_t line = __LINE__)
+            {
+                orig.dayOfGregorianCal = day;
+                assertPred!"=="(orig, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+
+            //Test B.C.
+            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            testST(SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+
+            //Test Both.
+            testST(SysTime(DateTime(-512, 7, 20, 0, 0, 0), FracSec.from!"hnsecs"(0)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(-513, 6, 6, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(-511, 5, 7, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 1, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+
+            testST(SysTime(DateTime(1607, 4, 8, 0, 0, 0), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(0, 12, 31, 0, 0, 0), FracSec.from!"hnsecs"(0)));
+            testST(SysTime(DateTime(1500, 3, 9, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            testST(SysTime(DateTime(999, 2, 10, 23, 59, 59), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
+            testST(SysTime(DateTime(2007, 12, 11, 23, 59, 59), FracSec.from!"hnsecs"(0)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
+
+
+            auto sysTime = SysTime(DateTime(1, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212));
+
+            void testST2(int day, in SysTime expected, size_t line = __LINE__)
+            {
+                sysTime.dayOfGregorianCal = day;
+                assertPred!"=="(sysTime, expected, "", __FILE__, line);
+            }
+
+            //Test A.D.
+            testST2(1, SysTime(DateTime(1, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(2, SysTime(DateTime(1, 1, 2, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(32, SysTime(DateTime(1, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(366, SysTime(DateTime(2, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(731, SysTime(DateTime(3, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(1096, SysTime(DateTime(4, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(1462, SysTime(DateTime(5, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(17_898, SysTime(DateTime(50, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(35_065, SysTime(DateTime(97, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(36_160, SysTime(DateTime(100, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(36_525, SysTime(DateTime(101, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(37_986, SysTime(DateTime(105, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(72_684, SysTime(DateTime(200, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(73_049, SysTime(DateTime(201, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(109_208, SysTime(DateTime(300, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(109_573, SysTime(DateTime(301, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(145_732, SysTime(DateTime(400, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(146_098, SysTime(DateTime(401, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(182_257, SysTime(DateTime(500, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(182_622, SysTime(DateTime(501, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(364_878, SysTime(DateTime(1000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(365_243, SysTime(DateTime(1001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(584_023, SysTime(DateTime(1600, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(584_389, SysTime(DateTime(1601, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(693_596, SysTime(DateTime(1900, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(693_961, SysTime(DateTime(1901, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(729_755, SysTime(DateTime(1999, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(730_120, SysTime(DateTime(2000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(730_486, SysTime(DateTime(2001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(733_773, SysTime(DateTime(2010, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_803, SysTime(DateTime(2010, 1, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_804, SysTime(DateTime(2010, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_831, SysTime(DateTime(2010, 2, 28, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_832, SysTime(DateTime(2010, 3, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_862, SysTime(DateTime(2010, 3, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_863, SysTime(DateTime(2010, 4, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_892, SysTime(DateTime(2010, 4, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_893, SysTime(DateTime(2010, 5, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_923, SysTime(DateTime(2010, 5, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_924, SysTime(DateTime(2010, 6, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_953, SysTime(DateTime(2010, 6, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_954, SysTime(DateTime(2010, 7, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_984, SysTime(DateTime(2010, 7, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(733_985, SysTime(DateTime(2010, 8, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_015, SysTime(DateTime(2010, 8, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_016, SysTime(DateTime(2010, 9, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_045, SysTime(DateTime(2010, 9, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_046, SysTime(DateTime(2010, 10, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_076, SysTime(DateTime(2010, 10, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_077, SysTime(DateTime(2010, 11, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_106, SysTime(DateTime(2010, 11, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_107, SysTime(DateTime(2010, 12, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_137, SysTime(DateTime(2010, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(734_534, SysTime(DateTime(2012, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_561, SysTime(DateTime(2012, 2, 28, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_562, SysTime(DateTime(2012, 2, 29, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_563, SysTime(DateTime(2012, 3, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(734_534,  SysTime(DateTime(2012, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(734_561, SysTime(DateTime(2012, 2, 28, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_562, SysTime(DateTime(2012, 2, 29, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(734_563, SysTime(DateTime(2012, 3, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            //Test B.C.
+            testST2(0, SysTime(DateTime(0, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1, SysTime(DateTime(0, 12, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-30, SysTime(DateTime(0, 12, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-31, SysTime(DateTime(0, 11, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(-366, SysTime(DateTime(-1, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-367, SysTime(DateTime(-1, 12, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-730, SysTime(DateTime(-1, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-731, SysTime(DateTime(-2, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1095, SysTime(DateTime(-2, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1096, SysTime(DateTime(-3, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1460, SysTime(DateTime(-3, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1461, SysTime(DateTime(-4, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1826, SysTime(DateTime(-4, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-1827, SysTime(DateTime(-5, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-2191, SysTime(DateTime(-5, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-3652, SysTime(DateTime(-9, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(-18_262, SysTime(DateTime(-49, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-18_627, SysTime(DateTime(-50, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-35_794, SysTime(DateTime(-97, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-36_160, SysTime(DateTime(-99, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-36_524, SysTime(DateTime(-99, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-36_889, SysTime(DateTime(-100, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-37_254, SysTime(DateTime(-101, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-38_715, SysTime(DateTime(-105, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-73_413, SysTime(DateTime(-200, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-73_778, SysTime(DateTime(-201, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-109_937, SysTime(DateTime(-300, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-110_302, SysTime(DateTime(-301, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-146_097, SysTime(DateTime(-400, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-146_462, SysTime(DateTime(-400, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-146_827, SysTime(DateTime(-401, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-182_621, SysTime(DateTime(-499, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-182_986, SysTime(DateTime(-500, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-183_351, SysTime(DateTime(-501, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-365_607, SysTime(DateTime(-1000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-365_972, SysTime(DateTime(-1001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-584_387, SysTime(DateTime(-1599, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-584_388, SysTime(DateTime(-1600, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-584_753, SysTime(DateTime(-1600, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-585_118, SysTime(DateTime(-1601, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-694_325, SysTime(DateTime(-1900, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-694_690, SysTime(DateTime(-1901, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-730_484, SysTime(DateTime(-1999, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-730_485, SysTime(DateTime(-2000, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-730_850, SysTime(DateTime(-2000, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-731_215, SysTime(DateTime(-2001, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(-734_502, SysTime(DateTime(-2010, 1, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_472, SysTime(DateTime(-2010, 1, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_471, SysTime(DateTime(-2010, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_444, SysTime(DateTime(-2010, 2, 28, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_443, SysTime(DateTime(-2010, 3, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_413, SysTime(DateTime(-2010, 3, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_412, SysTime(DateTime(-2010, 4, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_383, SysTime(DateTime(-2010, 4, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_382, SysTime(DateTime(-2010, 5, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_352, SysTime(DateTime(-2010, 5, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_351, SysTime(DateTime(-2010, 6, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_322, SysTime(DateTime(-2010, 6, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_321, SysTime(DateTime(-2010, 7, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_291, SysTime(DateTime(-2010, 7, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_290, SysTime(DateTime(-2010, 8, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_260, SysTime(DateTime(-2010, 8, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_259, SysTime(DateTime(-2010, 9, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_230, SysTime(DateTime(-2010, 9, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_229, SysTime(DateTime(-2010, 10, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_199, SysTime(DateTime(-2010, 10, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_198, SysTime(DateTime(-2010, 11, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_169, SysTime(DateTime(-2010, 11, 30, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_168, SysTime(DateTime(-2010, 12, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-734_138, SysTime(DateTime(-2010, 12, 31, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            testST2(-735_202, SysTime(DateTime(-2012, 2, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-735_175, SysTime(DateTime(-2012, 2, 28, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-735_174, SysTime(DateTime(-2012, 2, 29, 12, 2, 9), FracSec.from!"msecs"(212)));
+            testST2(-735_173, SysTime(DateTime(-2012, 3, 1, 12, 2, 9), FracSec.from!"msecs"(212)));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(!__traits(compiles, cst.dayOfGregorianCal = 7));
+            //static assert(!__traits(compiles, ist.dayOfGregorianCal = 7));
+
+            //Verify Examples.
+            auto st = SysTime(DateTime(0, 1, 1, 12, 0, 0));
+            st.dayOfGregorianCal = 1;
+            assert(st == SysTime(DateTime(1, 1, 1, 12, 0, 0)));
+
+            st.dayOfGregorianCal = 365;
+            assert(st == SysTime(DateTime(1, 12, 31, 12, 0, 0)));
+
+            st.dayOfGregorianCal = 366;
+            assert(st == SysTime(DateTime(2, 1, 1, 12, 0, 0)));
+
+            st.dayOfGregorianCal = 0;
+            assert(st == SysTime(DateTime(0, 12, 31, 12, 0, 0)));
+
+            st.dayOfGregorianCal = -365;
+            assert(st == SysTime(DateTime(-0, 1, 1, 12, 0, 0)));
+
+            st.dayOfGregorianCal = -366;
+            assert(st == SysTime(DateTime(-1, 12, 31, 12, 0, 0)));
+
+            st.dayOfGregorianCal = 730_120;
+            assert(st == SysTime(DateTime(2000, 1, 1, 12, 0, 0)));
+
+            st.dayOfGregorianCal = 734_137;
+            assert(st == SysTime(DateTime(2010, 12, 31, 12, 0, 0)));
+        }
+    }
+
+
+    /++
+        The ISO 8601 week of the year that this SysTime is in.
+
+        See_Also:
+            $(WEB en.wikipedia.org/wiki/ISO_week_date, ISO Week Date</a>
+      +/
+    @property ubyte isoWeek() const nothrow
+    {
+        return (cast(Date)this).isoWeek;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.isoWeek));
+            static assert(__traits(compiles, cst.isoWeek));
+            //static assert(__traits(compiles, ist.isoWeek));
+        }
+    }
+
+
+    /++
+        SysTime for the last day in the month that this Date is in.
+        The time portion of endOfMonth is always 23:59:59.9999999.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 1, 6, 0, 0, 0)).endOfMonth == SysTime(DateTime(1999, 1, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+assert(SysTime(DateTime(1999, 2, 7, 19, 30, 0), FracSec.from!"msecs"(24)).endOfMonth == SysTime(DateTime(1999, 2, 28, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+assert(SysTime(DateTime(2000, 2, 7, 5, 12, 27), FracSec.from!"usecs"(5203)).endOfMonth == SysTime(DateTime(2000, 2, 29, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+assert(SysTime(DateTime(2000, 6, 4, 12, 22, 9), FracSec.from!"hnsecs"(12345)).endOfMonth == SysTime(DateTime(2000, 6, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+--------------------
+      +/
+    @property SysTime endOfMonth() const nothrow
+    {
+        immutable hnsecs = adjTime;
+        immutable days = getUnitsFromHNSecs!"days"(hnsecs);
+
+        auto date = Date(cast(int)days + 1).endOfMonth;
+        auto newDays = date.dayOfGregorianCal - 1;
+        long theTimeHNSecs;
+
+        if(newDays < 0)
+        {
+            theTimeHNSecs = -1;
+            ++newDays;
+        }
+        else
+            theTimeHNSecs = convert!("days", "hnsecs")(1) - 1;
+
+        immutable newDaysHNSecs = convert!("days", "hnsecs")(newDays);
+
+        auto retval = SysTime(this._stdTime, this._timezone.get);
+        retval.adjTime = newDaysHNSecs + theTimeHNSecs;
+
+        return retval;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(Date(1999, 1, 1)).endOfMonth, SysTime(DateTime(1999, 1, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 2, 1)).endOfMonth, SysTime(DateTime(1999, 2, 28, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(2000, 2, 1)).endOfMonth, SysTime(DateTime(2000, 2, 29, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 3, 1)).endOfMonth, SysTime(DateTime(1999, 3, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 4, 1)).endOfMonth, SysTime(DateTime(1999, 4, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 5, 1)).endOfMonth, SysTime(DateTime(1999, 5, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 6, 1)).endOfMonth, SysTime(DateTime(1999, 6, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 7, 1)).endOfMonth, SysTime(DateTime(1999, 7, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 8, 1)).endOfMonth, SysTime(DateTime(1999, 8, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 9, 1)).endOfMonth, SysTime(DateTime(1999, 9, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 10, 1)).endOfMonth, SysTime(DateTime(1999, 10, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 11, 1)).endOfMonth, SysTime(DateTime(1999, 11, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(1999, 12, 1)).endOfMonth, SysTime(DateTime(1999, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+
+            //Test B.C.
+            assertPred!"=="(SysTime(Date(-1999, 1, 1)).endOfMonth, SysTime(DateTime(-1999, 1, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 2, 1)).endOfMonth, SysTime(DateTime(-1999, 2, 28, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-2000, 2, 1)).endOfMonth, SysTime(DateTime(-2000, 2, 29, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 3, 1)).endOfMonth, SysTime(DateTime(-1999, 3, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 4, 1)).endOfMonth, SysTime(DateTime(-1999, 4, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 5, 1)).endOfMonth, SysTime(DateTime(-1999, 5, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 6, 1)).endOfMonth, SysTime(DateTime(-1999, 6, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 7, 1)).endOfMonth, SysTime(DateTime(-1999, 7, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 8, 1)).endOfMonth, SysTime(DateTime(-1999, 8, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 9, 1)).endOfMonth, SysTime(DateTime(-1999, 9, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 10, 1)).endOfMonth, SysTime(DateTime(-1999, 10, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 11, 1)).endOfMonth, SysTime(DateTime(-1999, 11, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assertPred!"=="(SysTime(Date(-1999, 12, 1)).endOfMonth, SysTime(DateTime(-1999, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.endOfMonth));
+            //static assert(__traits(compiles, ist.endOfMonth));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 1, 6, 0, 0, 0)).endOfMonth == SysTime(DateTime(1999, 1, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assert(SysTime(DateTime(1999, 2, 7, 19, 30, 0), FracSec.from!"msecs"(24)).endOfMonth == SysTime(DateTime(1999, 2, 28, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assert(SysTime(DateTime(2000, 2, 7, 5, 12, 27), FracSec.from!"usecs"(5203)).endOfMonth == SysTime(DateTime(2000, 2, 29, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+            assert(SysTime(DateTime(2000, 6, 4, 12, 22, 9), FracSec.from!"hnsecs"(12345)).endOfMonth == SysTime(DateTime(2000, 6, 30, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
+        }
+    }
+
+
+    /++
+        The last day in the month that this SysTime is in.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1999, 1, 6, 0, 0, 0)).endOfMonthDay == 31);
+assert(SysTime(DateTime(1999, 2, 7, 19, 30, 0)).endOfMonthDay == 28);
+assert(SysTime(DateTime(2000, 2, 7, 5, 12, 27)).endOfMonthDay == 29);
+assert(SysTime(DateTime(2000, 6, 4, 12, 22, 9)).endOfMonthDay == 30);
+--------------------
+      +/
+    @property ubyte endOfMonthDay() const nothrow
+    {
+        return Date(dayOfGregorianCal).endOfMonthDay;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(DateTime(1999, 1, 1, 12, 1, 13)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 2, 1, 17, 13, 12)).endOfMonthDay, 28);
+            assertPred!"=="(SysTime(DateTime(2000, 2, 1, 13, 2, 12)).endOfMonthDay, 29);
+            assertPred!"=="(SysTime(DateTime(1999, 3, 1, 12, 13, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 4, 1, 12, 6, 13)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(1999, 5, 1, 15, 13, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 6, 1, 13, 7, 12)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(1999, 7, 1, 12, 13, 17)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 8, 1, 12, 3, 13)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 9, 1, 12, 13, 12)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(1999, 10, 1, 13, 19, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(1999, 11, 1, 12, 13, 17)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(1999, 12, 1, 12, 52, 13)).endOfMonthDay, 31);
+
+            //Test B.C.
+            assertPred!"=="(SysTime(DateTime(-1999, 1, 1, 12, 1, 13)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 2, 1, 7, 13, 12)).endOfMonthDay, 28);
+            assertPred!"=="(SysTime(DateTime(-2000, 2, 1, 13, 2, 12)).endOfMonthDay, 29);
+            assertPred!"=="(SysTime(DateTime(-1999, 3, 1, 12, 13, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 4, 1, 12, 6, 13)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(-1999, 5, 1, 5, 13, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 6, 1, 13, 7, 12)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(-1999, 7, 1, 12, 13, 17)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 8, 1, 12, 3, 13)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 9, 1, 12, 13, 12)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(-1999, 10, 1, 13, 19, 12)).endOfMonthDay, 31);
+            assertPred!"=="(SysTime(DateTime(-1999, 11, 1, 12, 13, 17)).endOfMonthDay, 30);
+            assertPred!"=="(SysTime(DateTime(-1999, 12, 1, 12, 52, 13)).endOfMonthDay, 31);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.endOfMonthDay));
+            //static assert(__traits(compiles, ist.endOfMonthDay));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1999, 1, 6, 0, 0, 0)).endOfMonthDay == 31);
+            assert(SysTime(DateTime(1999, 2, 7, 19, 30, 0)).endOfMonthDay == 28);
+            assert(SysTime(DateTime(2000, 2, 7, 5, 12, 27)).endOfMonthDay == 29);
+            assert(SysTime(DateTime(2000, 6, 4, 12, 22, 9)).endOfMonthDay == 30);
+        }
+    }
+
+
+    /++
+        Whether the current year is a date in A.D.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(1, 1, 1, 12, 7, 0)).isAD);
+assert(SysTime(DateTime(2010, 12, 31, 0, 0, 0)).isAD);
+assert(!SysTime(DateTime(0, 12, 31, 23, 59, 59)).isAD);
+assert(!SysTime(DateTime(-2010, 1, 1, 2, 2, 2)).isAD);
+--------------------
+      +/
+    @property bool isAD() const nothrow
+    {
+        return adjTime >= 0;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assert(SysTime(DateTime(2010, 7, 4, 12, 0, 9)).isAD);
+            assert(SysTime(DateTime(1, 1, 1, 0, 0, 0)).isAD);
+            assert(!SysTime(DateTime(0, 12, 31, 23, 59, 59)).isAD);
+            assert(!SysTime(DateTime(0, 1, 1, 23, 59, 59)).isAD);
+            assert(!SysTime(DateTime(-1, 1, 1, 23 ,59 ,59)).isAD);
+            assert(!SysTime(DateTime(-2010, 7, 4, 12, 2, 2)).isAD);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.isAD));
+            //static assert(__traits(compiles, ist.isAD));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(1, 1, 1, 12, 7, 0)).isAD);
+            assert(SysTime(DateTime(2010, 12, 31, 0, 0, 0)).isAD);
+            assert(!SysTime(DateTime(0, 12, 31, 23, 59, 59)).isAD);
+            assert(!SysTime(DateTime(-2010, 1, 1, 2, 2, 2)).isAD);
+        }
+    }
+
+
+    /++
+        The julian day for this SysTime at the given time. For example, prior
+        to noon, 1996-03-31 would be the julian day number 2_450_173, so this
+        function returns 2_450_173, while from noon onward, it the julian day
+        number would be 2_450_174, so this function returns 2_450_174.
+      +/
+    @property long julianDay() const nothrow
+    {
+        immutable jd = dayOfGregorianCal + 1_721_425;
+
+        return hour < 12 ? jd - 1 : jd;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime(-4713, 11, 24, 0, 0, 0)).julianDay, -1);
+            assertPred!"=="(SysTime(DateTime(-4713, 11, 24, 12, 0, 0)).julianDay, 0);
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 0, 0, 0)).julianDay, 1_721_424);
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 0, 0)).julianDay, 1_721_425);
+
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0)).julianDay, 1_721_425);
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 0, 0)).julianDay, 1_721_426);
+
+            assertPred!"=="(SysTime(DateTime(1582, 10, 15, 0, 0, 0)).julianDay, 2_299_160);
+            assertPred!"=="(SysTime(DateTime(1582, 10, 15, 12, 0, 0)).julianDay, 2_299_161);
+
+            assertPred!"=="(SysTime(DateTime(1858, 11, 17, 0, 0, 0)).julianDay, 2_400_000);
+            assertPred!"=="(SysTime(DateTime(1858, 11, 17, 12, 0, 0)).julianDay, 2_400_001);
+
+            assertPred!"=="(SysTime(DateTime(1982, 1, 4, 0, 0, 0)).julianDay, 2_444_973);
+            assertPred!"=="(SysTime(DateTime(1982, 1, 4, 12, 0, 0)).julianDay, 2_444_974);
+
+            assertPred!"=="(SysTime(DateTime(1996, 3, 31, 0, 0, 0)).julianDay, 2_450_173);
+            assertPred!"=="(SysTime(DateTime(1996, 3, 31, 12, 0, 0)).julianDay, 2_450_174);
+
+            assertPred!"=="(SysTime(DateTime(2010, 8, 24, 0, 0, 0)).julianDay, 2_455_432);
+            assertPred!"=="(SysTime(DateTime(2010, 8, 24, 12, 0, 0)).julianDay, 2_455_433);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.julianDay));
+            //static assert(__traits(compiles, ist.julianDay));
+        }
+    }
+
+
+    /++
+        The modified julian day for any time on this Date (since, the modified
+        julian day changes at midnight).
+      +/
+    @property long modJulianDay() const nothrow
+    {
+        return (dayOfGregorianCal + 1_721_425) - 2_400_001;
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(SysTime(DateTime(1858, 11, 17, 0, 0, 0)).modJulianDay, 0);
+            assertPred!"=="(SysTime(DateTime(1858, 11, 17, 12, 0, 0)).modJulianDay, 0);
+
+            assertPred!"=="(SysTime(DateTime(2010, 8, 24, 0, 0, 0)).modJulianDay, 55_432);
+            assertPred!"=="(SysTime(DateTime(2010, 8, 24, 12, 0, 0)).modJulianDay, 55_432);
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cst.modJulianDay));
+            //static assert(__traits(compiles, ist.modJulianDay));
+        }
+    }
+
+
+    /++
+        Returns a Date equivalent to this SysTime.
+      +/
+    Date opCast(T)() const nothrow
+        if(is(Unqual!T == Date))
+    {
+        return Date(dayOfGregorianCal);
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(cast(Date)SysTime(Date(1999, 7, 6)), Date(1999, 7, 6));
+            assertPred!"=="(cast(Date)SysTime(Date(2000, 12, 31)), Date(2000, 12, 31));
+            assertPred!"=="(cast(Date)SysTime(Date(2001, 1, 1)), Date(2001, 1, 1));
+
+            assertPred!"=="(cast(Date)SysTime(DateTime(1999, 7, 6, 12, 10, 9)), Date(1999, 7, 6));
+            assertPred!"=="(cast(Date)SysTime(DateTime(2000, 12, 31, 13, 11, 10)), Date(2000, 12, 31));
+            assertPred!"=="(cast(Date)SysTime(DateTime(2001, 1, 1, 14, 12, 11)), Date(2001, 1, 1));
+
+            assertPred!"=="(cast(Date)SysTime(Date(-1999, 7, 6)), Date(-1999, 7, 6));
+            assertPred!"=="(cast(Date)SysTime(Date(-2000, 12, 31)), Date(-2000, 12, 31));
+            assertPred!"=="(cast(Date)SysTime(Date(-2001, 1, 1)), Date(-2001, 1, 1));
+
+            assertPred!"=="(cast(Date)SysTime(DateTime(-1999, 7, 6, 12, 10, 9)), Date(-1999, 7, 6));
+            assertPred!"=="(cast(Date)SysTime(DateTime(-2000, 12, 31, 13, 11, 10)), Date(-2000, 12, 31));
+            assertPred!"=="(cast(Date)SysTime(DateTime(-2001, 1, 1, 14, 12, 11)), Date(-2001, 1, 1));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(Date)cst));
+            //static assert(__traits(compiles, cast(Date)ist));
+        }
+    }
+
+
+    /++
+        Returns a DateTime equivalent to this SysTime.
+      +/
+    DateTime opCast(T)() const nothrow
+        if(is(Unqual!T == DateTime))
+    {
+        try
+        {
+            auto hnsecs = adjTime;
+            auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+            if(hnsecs < 0)
+            {
+                hnsecs += convert!("hours", "hnsecs")(24);
+                --days;
+            }
+
+            immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            immutable second = getUnitsFromHNSecs!"seconds"(hnsecs);
+
+            return DateTime(Date(cast(int)days), TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second));
+        }
+        catch(Exception e)
+            assert(0, "Either DateTime's constructor or TimeOfDay's constructor threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(1, 1, 6, 7, 12, 22)), DateTime(1, 1, 6, 7, 12, 22));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(1, 1, 6, 7, 12, 22), FracSec.from!"msecs"(22)), DateTime(1, 1, 6, 7, 12, 22));
+            assertPred!"=="(cast(DateTime)SysTime(Date(1999, 7, 6)), DateTime(1999, 7, 6, 0, 0, 0));
+            assertPred!"=="(cast(DateTime)SysTime(Date(2000, 12, 31)), DateTime(2000, 12, 31, 0, 0, 0));
+            assertPred!"=="(cast(DateTime)SysTime(Date(2001, 1, 1)), DateTime(2001, 1, 1, 0, 0, 0));
+
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(1999, 7, 6, 12, 10, 9)), DateTime(1999, 7, 6, 12, 10, 9));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(2000, 12, 31, 13, 11, 10)), DateTime(2000, 12, 31, 13, 11, 10));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(2001, 1, 1, 14, 12, 11)), DateTime(2001, 1, 1, 14, 12, 11));
+
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(-1, 1, 6, 7, 12, 22)), DateTime(-1, 1, 6, 7, 12, 22));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(-1, 1, 6, 7, 12, 22), FracSec.from!"msecs"(22)), DateTime(-1, 1, 6, 7, 12, 22));
+            assertPred!"=="(cast(DateTime)SysTime(Date(-1999, 7, 6)), DateTime(-1999, 7, 6, 0, 0, 0));
+            assertPred!"=="(cast(DateTime)SysTime(Date(-2000, 12, 31)), DateTime(-2000, 12, 31, 0, 0, 0));
+            assertPred!"=="(cast(DateTime)SysTime(Date(-2001, 1, 1)), DateTime(-2001, 1, 1, 0, 0, 0));
+
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(-1999, 7, 6, 12, 10, 9)), DateTime(-1999, 7, 6, 12, 10, 9));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(-2000, 12, 31, 13, 11, 10)), DateTime(-2000, 12, 31, 13, 11, 10));
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(-2001, 1, 1, 14, 12, 11)), DateTime(-2001, 1, 1, 14, 12, 11));
+
+            assertPred!"=="(cast(DateTime)SysTime(DateTime(2011, 1, 13, 8, 17, 2), FracSec.from!"msecs"(296), LocalTime()),
+                            DateTime(2011, 1, 13, 8, 17, 2));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(DateTime)cst));
+            //static assert(__traits(compiles, cast(DateTime)ist));
+        }
+    }
+
+
+    /++
+        Returns a TimeOfDay equivalent to this SysTime.
+      +/
+    TimeOfDay opCast(T)() const nothrow
+        if(is(Unqual!T == TimeOfDay))
+    {
+        try
+        {
+            auto hnsecs = adjTime;
+            hnsecs = removeUnitsFromHNSecs!"days"(hnsecs);
+
+            if(hnsecs < 0)
+                hnsecs += convert!("hours", "hnsecs")(24);
+
+            immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            immutable second = getUnitsFromHNSecs!"seconds"(hnsecs);
+
+            return TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second);
+        }
+        catch(Exception e)
+            assert(0, "TimeOfDay's constructor threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(1999, 7, 6)), TimeOfDay(0, 0, 0));
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(2000, 12, 31)), TimeOfDay(0, 0, 0));
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(2001, 1, 1)), TimeOfDay(0, 0, 0));
+
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(1999, 7, 6, 12, 10, 9)), TimeOfDay(12, 10, 9));
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(2000, 12, 31, 13, 11, 10)), TimeOfDay(13, 11, 10));
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(2001, 1, 1, 14, 12, 11)), TimeOfDay(14, 12, 11));
+
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(-1999, 7, 6)), TimeOfDay(0, 0, 0));
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(-2000, 12, 31)), TimeOfDay(0, 0, 0));
+            assertPred!"=="(cast(TimeOfDay)SysTime(Date(-2001, 1, 1)), TimeOfDay(0, 0, 0));
+
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(-1999, 7, 6, 12, 10, 9)), TimeOfDay(12, 10, 9));
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(-2000, 12, 31, 13, 11, 10)), TimeOfDay(13, 11, 10));
+            assertPred!"=="(cast(TimeOfDay)SysTime(DateTime(-2001, 1, 1, 14, 12, 11)), TimeOfDay(14, 12, 11));
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(TimeOfDay)cst));
+            //static assert(__traits(compiles, cast(TimeOfDay)ist));
+        }
+    }
+
+
+    //Temporary hack until bug http://d.puremagic.com/issues/show_bug.cgi?id=4867 is fixed.
+    //This allows assignment from const(SysTime) to SysTime.
+    //It may be a good idea to keep it though, since casting from a type to itself
+    //should be allowed, and it doesn't work without this opCast() since opCast()
+    //has already been defined for other types.
+    SysTime opCast(T)() const pure nothrow
+        if(is(Unqual!T == SysTime))
+    {
+        return SysTime(_stdTime, _timezone.get);
+    }
+
+
+    /++
+        Converts this SysTime to a string with the format YYYYMMDDTHHMMSS.FFFFFFFTZ
+        (where F is fractional seconds and TZ is time zone).
+
+        Note that the number of digits in the fractional seconds varies with the
+        number of fractional seconds. It's a maximum of 7 (which would be hnsecs),
+        but only has as many as are necessary to hold the correct value (so no
+        trailing zeroes), and if there are no fractional seconds, then there is
+        no decimal point.
+
+        If this SysTime's time zone is LocalTime, then TZ is empty. If the time zone
+        is UTC, then it is "Z". Otherwise, it is the offset from UTC (e.g. +1:00 or -7:00).
+        Note that the offset from UTC is $(I not) enough to uniquely identify the time zone.
+
+        Time zone offsets will be in the form +HH:MM or -HH:MM.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toISOString() ==
+       "20100704T070612");
+assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toISOString() ==
+       "19981225T021500.024");
+assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toISOString() ==
+       "00000105T230959");
+assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toISOString() ==
+       "-00040105T000002.052092");
+--------------------
+      +/
+    string toISOString() const nothrow
+    {
+        try
+        {
+            immutable adjustedTime = adjTime;
+            long hnsecs = adjustedTime;
+
+            auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+            if(hnsecs < 0)
+            {
+                hnsecs += convert!("hours", "hnsecs")(24);
+                --days;
+            }
+
+            auto hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            auto minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            auto second = splitUnitsFromHNSecs!"seconds"(hnsecs);
+
+            auto dateTime = DateTime(Date(cast(int)days), TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second));
+            auto fracSecStr = fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is LocalTime())
+                return dateTime.toISOString() ~ fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is UTC())
+                return dateTime.toISOString() ~ fracSecToISOString(cast(int)hnsecs) ~ "Z";
+
+            immutable utcOffset = cast(int)convert!("hnsecs", "minutes")(stdTime - adjustedTime);
+
+            return dateTime.toISOString() ~ fracSecToISOString(cast(int)hnsecs) ~ SimpleTimeZone.toISOString(utcOffset);
+        }
+        catch(Exception e)
+            assert(0, "format() threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(DateTime.init, UTC()).toISOString(), "00010101T000000Z");
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1), UTC()).toISOString(), "00010101T000000.0000001Z");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0)).toISOString(), "00091204T000000");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12)).toISOString(), "00991204T050612");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59)).toISOString(), "09991204T134459");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59)).toISOString(), "99990704T235959");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1)).toISOString(), "+100001020T010101");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toISOString(), "00091204T000000.042");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toISOString(), "00991204T050612.1");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toISOString(), "09991204T134459.04502");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toISOString(), "99990704T235959.0000012");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toISOString(), "+100001020T010101.050789");
+
+            //Test B.C.
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toISOString(), "00001231T235959.9999999Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1), UTC()).toISOString(), "00001231T235959.0000001Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), UTC()).toISOString(), "00001231T235959Z");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 12, 4)).toISOString(), "00001204T001204");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0)).toISOString(), "-00091204T000000");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12)).toISOString(), "-00991204T050612");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59)).toISOString(), "-09991204T134459");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59)).toISOString(), "-99990704T235959");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1)).toISOString(), "-100001020T010101");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 0, 0), FracSec.from!"msecs"(7)).toISOString(), "00001204T000000.007");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toISOString(), "-00091204T000000.042");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toISOString(), "-00991204T050612.1");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toISOString(), "-09991204T134459.04502");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toISOString(), "-99990704T235959.0000012");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toISOString(), "-100001020T010101.050789");
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(TimeOfDay)cst));
+            //static assert(__traits(compiles, cast(TimeOfDay)ist));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toISOString() == "20100704T070612");
+            assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toISOString() == "19981225T021500.024");
+            assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toISOString() == "00000105T230959");
+            assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toISOString() == "-00040105T000002.052092");
+        }
+    }
+
+
+
+    /++
+        Converts this SysTime to a string with the format YYYY-MM-DDTHH:MM:SS.FFFFFFFTZ
+        (where F is fractional seconds and TZ is time zone).
+
+        Note that the number of digits in the fractional seconds varies with the
+        number of fractional seconds. It's a maximum of 7 (which would be hnsecs),
+        but only has as many as are necessary to hold the correct value (so no
+        trailing zeroes), and if there are no fractional seconds, then there is
+        no decimal point.
+
+        If this SysTime's time zone is LocalTime, then TZ is empty. If the time
+        zone is UTC, then it is "Z". Otherwise, it is the offset from UTC
+        (e.g. +1:00 or -7:00). Note that the offset from UTC is $(I not) enough
+        to uniquely identify the time zone.
+
+        Time zone offsets will be in the form +HH:MM or -HH:MM.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toISOExtendedString() ==
+       "2010-07-04T07:06:12");
+assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toISOExtendedString() ==
+       "1998-12-25T02:15:00.024");
+assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toISOExtendedString() ==
+       "0000-01-05T23:09:59");
+assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toISOExtendedString() ==
+       "-0004-01-05T00:00:02.052092");
+--------------------
+      +/
+    string toISOExtendedString() const nothrow
+    {
+        try
+        {
+            immutable adjustedTime = adjTime;
+            long hnsecs = adjustedTime;
+
+            auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+            if(hnsecs < 0)
+            {
+                hnsecs += convert!("hours", "hnsecs")(24);
+                --days;
+            }
+
+            auto hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            auto minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            auto second = splitUnitsFromHNSecs!"seconds"(hnsecs);
+
+            auto dateTime = DateTime(Date(cast(int)days), TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second));
+            auto fracSecStr = fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is LocalTime())
+                return dateTime.toISOExtendedString() ~ fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is UTC())
+                return dateTime.toISOExtendedString() ~ fracSecToISOString(cast(int)hnsecs) ~ "Z";
+
+            immutable utcOffset = cast(int)convert!("hnsecs", "minutes")(stdTime - adjustedTime);
+
+            return dateTime.toISOExtendedString() ~ fracSecToISOString(cast(int)hnsecs) ~ SimpleTimeZone.toISOString(utcOffset);
+        }
+        catch(Exception e)
+            assert(0, "format() threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(DateTime.init, UTC()).toISOExtendedString(), "0001-01-01T00:00:00Z");
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1), UTC()).toISOExtendedString(), "0001-01-01T00:00:00.0000001Z");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0)).toISOExtendedString(), "0009-12-04T00:00:00");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12)).toISOExtendedString(), "0099-12-04T05:06:12");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59)).toISOExtendedString(), "0999-12-04T13:44:59");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59)).toISOExtendedString(), "9999-07-04T23:59:59");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1)).toISOExtendedString(), "+10000-10-20T01:01:01");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toISOExtendedString(), "0009-12-04T00:00:00.042");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toISOExtendedString(), "0099-12-04T05:06:12.1");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toISOExtendedString(), "0999-12-04T13:44:59.04502");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toISOExtendedString(), "9999-07-04T23:59:59.0000012");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toISOExtendedString(), "+10000-10-20T01:01:01.050789");
+
+            //Test B.C.
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toISOExtendedString(), "0000-12-31T23:59:59.9999999Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1), UTC()).toISOExtendedString(), "0000-12-31T23:59:59.0000001Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), UTC()).toISOExtendedString(), "0000-12-31T23:59:59Z");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 12, 4)).toISOExtendedString(), "0000-12-04T00:12:04");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0)).toISOExtendedString(), "-0009-12-04T00:00:00");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12)).toISOExtendedString(), "-0099-12-04T05:06:12");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59)).toISOExtendedString(), "-0999-12-04T13:44:59");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59)).toISOExtendedString(), "-9999-07-04T23:59:59");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1)).toISOExtendedString(), "-10000-10-20T01:01:01");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 0, 0), FracSec.from!"msecs"(7)).toISOExtendedString(), "0000-12-04T00:00:00.007");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toISOExtendedString(), "-0009-12-04T00:00:00.042");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toISOExtendedString(), "-0099-12-04T05:06:12.1");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toISOExtendedString(), "-0999-12-04T13:44:59.04502");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toISOExtendedString(), "-9999-07-04T23:59:59.0000012");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toISOExtendedString(), "-10000-10-20T01:01:01.050789");
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(TimeOfDay)cst));
+            //static assert(__traits(compiles, cast(TimeOfDay)ist));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toISOExtendedString() == "2010-07-04T07:06:12");
+            assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toISOExtendedString() == "1998-12-25T02:15:00.024");
+            assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toISOExtendedString() == "0000-01-05T23:09:59");
+            assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toISOExtendedString() == "-0004-01-05T00:00:02.052092");
+        }
+    }
+
+    /++
+        Converts this SysTime to a string with the format YYYY-Mon-DD HH:MM:SS.FFFFFFFTZ
+        (where F is fractional seconds and TZ is time zone).
+
+        Note that the number of digits in the fractional seconds varies with the
+        number of fractional seconds. It's a maximum of 7 (which would be hnsecs),
+        but only has as many as are necessary to hold the correct value (so no
+        trailing zeroes), and if there are no fractional seconds, then there is
+        no decimal point.
+
+        If this SysTime's time zone is LocalTime, then TZ is empty. If the time
+        zone is UTC, then it is "Z". Otherwise, it is the offset from UTC
+        (e.g. +1:00 or -7:00). Note that the offset from UTC is $(I not) enough
+        to uniquely identify the time zone.
+
+        Time zone offsets will be in the form +HH:MM or -HH:MM.
+
+        Examples:
+--------------------
+assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toSimpleString() ==
+       "2010-Jul-04 07:06:12");
+assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toSimpleString() ==
+       "1998-Dec-25 02:15:00.024");
+assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toSimpleString() ==
+       "0000-Jan-05 23:09:59");
+assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toSimpleString() ==
+        "-0004-Jan-05 00:00:02.052092");
+--------------------
+      +/
+    string toSimpleString() const nothrow
+    {
+        try
+        {
+            immutable adjustedTime = adjTime;
+            long hnsecs = adjustedTime;
+
+            auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
+
+            if(hnsecs < 0)
+            {
+                hnsecs += convert!("hours", "hnsecs")(24);
+                --days;
+            }
+
+            auto hour = splitUnitsFromHNSecs!"hours"(hnsecs);
+            auto minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
+            auto second = splitUnitsFromHNSecs!"seconds"(hnsecs);
+
+            auto dateTime = DateTime(Date(cast(int)days), TimeOfDay(cast(int)hour, cast(int)minute, cast(int)second));
+            auto fracSecStr = fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is LocalTime())
+                return dateTime.toSimpleString() ~ fracSecToISOString(cast(int)hnsecs);
+
+            if(_timezone.get is UTC())
+                return dateTime.toSimpleString() ~ fracSecToISOString(cast(int)hnsecs) ~ "Z";
+
+            immutable utcOffset = cast(int)convert!("hnsecs", "minutes")(stdTime - adjustedTime);
+
+            return dateTime.toSimpleString() ~ fracSecToISOString(cast(int)hnsecs) ~ SimpleTimeZone.toISOString(utcOffset);
+        }
+        catch(Exception e)
+            assert(0, "format() threw.");
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            //Test A.D.
+            assertPred!"=="(SysTime(DateTime.init, UTC()).toString(), "0001-Jan-01 00:00:00Z");
+            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1), UTC()).toString(), "0001-Jan-01 00:00:00.0000001Z");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0)).toSimpleString(), "0009-Dec-04 00:00:00");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12)).toSimpleString(), "0099-Dec-04 05:06:12");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59)).toSimpleString(), "0999-Dec-04 13:44:59");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59)).toSimpleString(), "9999-Jul-04 23:59:59");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1)).toSimpleString(), "+10000-Oct-20 01:01:01");
+
+            assertPred!"=="(SysTime(DateTime(9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toSimpleString(), "0009-Dec-04 00:00:00.042");
+            assertPred!"=="(SysTime(DateTime(99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toSimpleString(), "0099-Dec-04 05:06:12.1");
+            assertPred!"=="(SysTime(DateTime(999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toSimpleString(), "0999-Dec-04 13:44:59.04502");
+            assertPred!"=="(SysTime(DateTime(9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toSimpleString(), "9999-Jul-04 23:59:59.0000012");
+            assertPred!"=="(SysTime(DateTime(10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toSimpleString(), "+10000-Oct-20 01:01:01.050789");
+
+            //Test B.C.
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toSimpleString(), "0000-Dec-31 23:59:59.9999999Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1), UTC()).toSimpleString(), "0000-Dec-31 23:59:59.0000001Z");
+            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), UTC()).toSimpleString(), "0000-Dec-31 23:59:59Z");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 12, 4)).toSimpleString(), "0000-Dec-04 00:12:04");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0)).toSimpleString(), "-0009-Dec-04 00:00:00");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12)).toSimpleString(), "-0099-Dec-04 05:06:12");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59)).toSimpleString(), "-0999-Dec-04 13:44:59");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59)).toSimpleString(), "-9999-Jul-04 23:59:59");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1)).toSimpleString(), "-10000-Oct-20 01:01:01");
+
+            assertPred!"=="(SysTime(DateTime(0, 12, 4, 0, 0, 0), FracSec.from!"msecs"(7)).toSimpleString(), "0000-Dec-04 00:00:00.007");
+            assertPred!"=="(SysTime(DateTime(-9, 12, 4, 0, 0, 0), FracSec.from!"msecs"(42)).toSimpleString(), "-0009-Dec-04 00:00:00.042");
+            assertPred!"=="(SysTime(DateTime(-99, 12, 4, 5, 6, 12), FracSec.from!"msecs"(100)).toSimpleString(), "-0099-Dec-04 05:06:12.1");
+            assertPred!"=="(SysTime(DateTime(-999, 12, 4, 13, 44, 59), FracSec.from!"usecs"(45020)).toSimpleString(), "-0999-Dec-04 13:44:59.04502");
+            assertPred!"=="(SysTime(DateTime(-9999, 7, 4, 23, 59, 59), FracSec.from!"hnsecs"(12)).toSimpleString(), "-9999-Jul-04 23:59:59.0000012");
+            assertPred!"=="(SysTime(DateTime(-10000, 10, 20, 1, 1, 1), FracSec.from!"hnsecs"(507890)).toSimpleString(), "-10000-Oct-20 01:01:01.050789");
+
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, cast(TimeOfDay)cst));
+            //static assert(__traits(compiles, cast(TimeOfDay)ist));
+
+            //Verify Examples.
+            assert(SysTime(DateTime(2010, 7, 4, 7, 6, 12)).toSimpleString() == "2010-Jul-04 07:06:12");
+            assert(SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(24)).toSimpleString() == "1998-Dec-25 02:15:00.024");
+            assert(SysTime(DateTime(0, 1, 5, 23, 9, 59)).toSimpleString() == "0000-Jan-05 23:09:59");
+            assert(SysTime(DateTime(-4, 1, 5, 0, 0, 2), FracSec.from!"hnsecs"(520920)).toSimpleString() == "-0004-Jan-05 00:00:02.052092");
+        }
+    }
+
+
+    /+
+        Converts this SysTime to a string.
+      +/
+    //Due to bug http://d.puremagic.com/issues/show_bug.cgi?id=3715 , we can't
+    //have versions of toString() with extra modifiers, so we define one version
+    //with modifiers and one without.
+    string toString()
+    {
+        return toSimpleString();
+    }
+
+    /++
+        Converts this SysTime to a string.
+      +/
+    //Due to bug http://d.puremagic.com/issues/show_bug.cgi?id=3715 , we can't
+    //have versions of toString() with extra modifiers, so we define one version
+    //with modifiers and one without.
+    string toString() const nothrow
+    {
+        return toSimpleString();
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
+            static assert(__traits(compiles, st.toString()));
+            static assert(__traits(compiles, cst.toString()));
+            //static assert(__traits(compiles, ist.toString()));
+        }
+    }
+
+
+    /++
+        Creates a SysTime from a string with the format YYYYMMDDTHHMMSS.FFFFFFFTZ
+        (where F is fractional seconds is time zone). Whitespace is stripped from
+        the given string.
+
+        The exact format is exactly as described in toISOString() except that
+        trailing zeroes are permitted - including having fractional seconds with
+        all zeroes. However, a decimal point with nothing following it is invalid.
+
+        If there is no time zone in the string, then LocalTime is used. If the
+        time zone is "Z", then UTC is used. Otherwise, a SimpleTimeZone which
+        corresponds to the given offset from UTC is used. If you wish the
+        returned SysTime to be a particular time zone, then pass in that time
+        zone and the SysTime to be returned will be converted to that time zone
+        (though it will still be read in as whatever time zone is in its string).
+
+        The accepted formats for time zone offsets are +H, -H, +HH, -HH, +H:MM,
+        -H:MM, +HH:MM, and -HH:MM.
+
+        Params:
+            isoString = A string formatted in the ISO format for dates and times.
+            tz        = The time zone to convert the given time to (no conversion
+                        occurs if null).
+
+        Throws:
+            DateTimeException if the given string is not in the ISO format or if
+            the resulting SysTime would not be valid.
+
+        Examples:
+--------------------
+assert(SysTime.fromISOString("20100704T070612") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+assert(SysTime.fromISOString("19981225T021500.007") ==
+       SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+assert(SysTime.fromISOString("00000105T230959.00002") ==
+       SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+assert(SysTime.fromISOString("-00040105T000002") ==
+       SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+assert(SysTime.fromISOString(" 20100704T070612 ") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+assert(SysTime.fromISOString("20100704T070612Z") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+assert(SysTime.fromISOString("20100704T070612-8:00") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+assert(SysTime.fromISOString("20100704T070612+8:00") ==
+       SysTime(DateTime(2010, 7, 3, 7, 6, 12), new SimpleTimeZone(480)));
+--------------------
+      +/
+    static SysTime fromISOString(S)(in S isoString, immutable TimeZone tz = null)
+        if(isSomeString!S)
+    {
+        auto dstr = to!dstring(strip(isoString));
+        immutable skipFirst = dstr.startsWith("+", "-") != 0;
+
+        auto found = (skipFirst ? dstr[1..$] : dstr).find(".", "Z", "+", "-");
+        auto dateTimeStr = dstr[0 .. $ - found[0].length];
+
+        dstring fracSecStr;
+        dstring zoneStr;
+
+        if(found[1] != 0)
+        {
+            if(found[1] == 1)
+            {
+                auto foundTZ = found[0].find("Z", "+", "-");
+
+                if(foundTZ[1] != 0)
+                {
+                    fracSecStr = found[0][0 .. $ - foundTZ[0].length];
+                    zoneStr = foundTZ[0];
+                }
+                else
+                    fracSecStr = found[0];
+            }
+            else
+                zoneStr = found[0];
+        }
+
+        try
+        {
+            auto dateTime = DateTime.fromISOString(dateTimeStr);
+            auto fracSec = fracSecFromISOString(fracSecStr);
+            DTRebindable!(immutable TimeZone) parsedZone;
+
+            if(zoneStr.empty)
+                parsedZone = LocalTime();
+            else if(zoneStr == "Z")
+                parsedZone = UTC();
+            else
+                parsedZone = SimpleTimeZone.fromISOString(zoneStr);
+
+            auto retval = SysTime(dateTime, fracSec, parsedZone.get);
+
+            if(tz !is null)
+                retval.timezone = tz;
+
+            return retval;
+        }
+        catch(DateTimeException dte)
+            throw new DateTimeException(format("Invalid ISO String: %s", isoString));
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertThrown!DateTimeException(SysTime.fromISOString(""));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704000000"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704 000000"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704t000000"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000."));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000.A"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000.Z"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000.00000000"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000.00000000"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000+"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000-"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000:"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000-:"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000+:"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000-1:"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000+1:"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000+1:0"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000-24.00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("20100704T000000+24.00"));
+
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-07-0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-07-04 00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-07-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-07-04T00:00:00."));
+
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Jul-0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Jul-04 00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Jul-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Jul-04T00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Jul-04 00:00:00."));
+
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-12-22T172201"));
+            assertThrown!DateTimeException(SysTime.fromISOString("2010-Dec-22 17:22:01"));
+
+            assertPred!"=="(SysTime.fromISOString("20101222T172201"), SysTime(DateTime(2010, 12, 22, 17, 22, 01)));
+            assertPred!"=="(SysTime.fromISOString("19990706T123033"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOString("-19990706T123033"), SysTime(DateTime(-1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOString("+019990706T123033"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOString("19990706T123033 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOString(" 19990706T123033"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOString(" 19990706T123033 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.0"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.0000000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.0000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"hnsecs"(1)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.0000010"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+            assertPred!"=="(SysTime.fromISOString("19070707T121212.0010000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+
+            assertPred!"=="(SysTime.fromISOString("20101222T172201Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), UTC()));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(480)));
+
+            assertPred!"=="(SysTime.fromISOString("20101103T065106.57159Z"), SysTime(DateTime(2010, 11, 3, 6, 51, 6), FracSec.from!"hnsecs"(5715900), UTC()));
+
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.23412Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_341_200), UTC()));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.23112-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_311_200), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.45-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.1-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_000_000), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.55-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(5_500_000), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.1234567+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_234_567), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.0+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.0000000+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromISOString("20101222T172201.45+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(480)));
+
+            //Verify Examples.
+            assert(SysTime.fromISOString("20100704T070612") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+            assert(SysTime.fromISOString("19981225T021500.007") == SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+            assert(SysTime.fromISOString("00000105T230959.00002") == SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+            assert(SysTime.fromISOString("-00040105T000002") == SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+            assert(SysTime.fromISOString(" 20100704T070612 ") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+            assert(SysTime.fromISOString("20100704T070612Z") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+            assert(SysTime.fromISOString("20100704T070612-8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+            assert(SysTime.fromISOString("20100704T070612+8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(480)));
+        }
+    }
+
+
+    /++
+        Creates a SysTime from a string with the format YYYY-MM-DDTHH:MM:SS.FFFFFFFTZ
+        (where F is fractional seconds is time zone). Whitespace is stripped from the
+        given string.
+
+        The exact format is exactly as described in toISOExtendedString() except
+        that trailing zeroes are permitted - including having fractional seconds
+        with all zeroes. However, a decimal point with nothing following it is
+        invalid.
+
+        If there is no time zone in the string, then LocalTime is used. If the
+        time zone is "Z", then UTC is used. Otherwise, a SimpleTimeZone which
+        corresponds to the given offset from UTC is used. If you wish the
+        returned SysTime to be a particular time zone, then pass in that time
+        zone and the SysTime to be returned will be converted to that time zone
+        (though it will still be read in as whatever time zone is in its string).
+
+        The accepted formats for time zone offsets are +H, -H, +HH, -HH, +H:MM,
+        -H:MM, +HH:MM, and -HH:MM.
+
+        Params:
+            isoString = A string formatted in the ISO Extended format for dates
+                        and times.
+            tz        = The time zone to convert the given time to (no conversion
+                        occurs if null).
+
+        Throws:
+            DateTimeException if the given string is not in the ISO format or if
+            the resulting SysTime would not be valid.
+
+        Examples:
+--------------------
+assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+assert(SysTime.fromISOExtendedString("1998-12-25T02:15:00.007") ==
+       SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+assert(SysTime.fromISOExtendedString("0000-01-05T23:09:59.00002") ==
+       SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+assert(SysTime.fromISOExtendedString("-0004-01-05T00:00:02") ==
+       SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+assert(SysTime.fromISOExtendedString(" 2010-07-04T07:06:12 ") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12Z") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12-8:00") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12+8:00") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(480)));
+--------------------
+      +/
+    static SysTime fromISOExtendedString(S)(in S isoExtString, immutable TimeZone tz = null)
+        if(isSomeString!(S))
+    {
+        auto dstr = to!dstring(strip(isoExtString));
+
+        auto tIndex = dstr.indexOf("T");
+        enforce(tIndex != -1, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
+
+        auto found = dstr[tIndex + 1 .. $].find(".", "Z", "+", "-");
+        auto dateTimeStr = dstr[0 .. $ - found[0].length];
+
+        dstring fracSecStr;
+        dstring zoneStr;
+
+        if(found[1] != 0)
+        {
+            if(found[1] == 1)
+            {
+                auto foundTZ = found[0].find("Z", "+", "-");
+
+                if(foundTZ[1] != 0)
+                {
+                    fracSecStr = found[0][0 .. $ - foundTZ[0].length];
+                    zoneStr = foundTZ[0];
+                }
+                else
+                    fracSecStr = found[0];
+            }
+            else
+                zoneStr = found[0];
+        }
+
+        try
+        {
+            auto dateTime = DateTime.fromISOExtendedString(dateTimeStr);
+            auto fracSec = fracSecFromISOString(fracSecStr);
+            DTRebindable!(immutable TimeZone) parsedZone;
+
+            if(zoneStr.empty)
+                parsedZone = LocalTime();
+            else if(zoneStr == "Z")
+                parsedZone = UTC();
+            else
+                parsedZone = SimpleTimeZone.fromISOString(zoneStr);
+
+            auto retval = SysTime(dateTime, fracSec, parsedZone.get);
+
+            if(tz !is null)
+                retval.timezone = tz;
+
+            return retval;
+        }
+        catch(DateTimeException dte)
+            throw new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString));
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString(""));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20100704000000"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20100704 000000"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20100704t000000"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20100704T000000."));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20100704T000000.0"));
+
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07:0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04 00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04 00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00."));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00.A"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00.Z"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00.00000000"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00.00000000"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00+"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00-"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00:"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00-:"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00+:"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00-1:"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00+1:"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00+1:0"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00-24.00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-07-04T00:00:00+24.00"));
+
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-Jul-0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-Jul-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-Jul-04 00:00:00."));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-Jul-04 00:00:00.0"));
+
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("20101222T172201"));
+            assertThrown!DateTimeException(SysTime.fromISOExtendedString("2010-Dec-22 17:22:01"));
+
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01"), SysTime(DateTime(2010, 12, 22, 17, 22, 01)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1999-07-06T12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOExtendedString("-1999-07-06T12:30:33"), SysTime(DateTime(-1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOExtendedString("+01999-07-06T12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1999-07-06T12:30:33 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOExtendedString(" 1999-07-06T12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromISOExtendedString(" 1999-07-06T12:30:33 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.0"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.0000000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.0000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"hnsecs"(1)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.0000010"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+            assertPred!"=="(SysTime.fromISOExtendedString("1907-07-07T12:12:12.0010000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), UTC()));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(480)));
+
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-11-03T06:51:06.57159Z"), SysTime(DateTime(2010, 11, 3, 6, 51, 6), FracSec.from!"hnsecs"(5715900), UTC()));
+
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.23412Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_341_200), UTC()));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.23112-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_311_200), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.45-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.1-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_000_000), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.55-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(5_500_000), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.1234567+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_234_567), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.0+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.0000000+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromISOExtendedString("2010-12-22T17:22:01.45+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(480)));
+
+            //Verify Examples.
+            assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+            assert(SysTime.fromISOExtendedString("1998-12-25T02:15:00.007") == SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+            assert(SysTime.fromISOExtendedString("0000-01-05T23:09:59.00002") == SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+            assert(SysTime.fromISOExtendedString("-0004-01-05T00:00:02") == SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+            assert(SysTime.fromISOExtendedString(" 2010-07-04T07:06:12 ") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+            assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12Z") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+            assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12-8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+            assert(SysTime.fromISOExtendedString("2010-07-04T07:06:12+8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(480)));
+        }
+    }
+
+
+    /++
+        Creates a SysTime from a string with the format YYYY-MM-DD HH:MM:SS.FFFFFFFTZ
+        (where F is fractional seconds is time zone). Whitespace is stripped from the
+        given string.
+
+        The exact format is exactly as described in toSimpleString() except that
+        trailing zeroes are permitted - including having fractional seconds with
+        all zeroes. However, a decimal point with nothing following it is invalid.
+
+        If there is no time zone in the string, then LocalTime is used. If the
+        time zone is "Z", then UTC is used. Otherwise, a SimpleTimeZone which
+        corresponds to the given offset from UTC is used. If you wish the
+        returned SysTime to be a particular time zone, then pass in that time
+        zone and the SysTime to be returned will be converted to that time zone
+        (though it will still be read in as whatever time zone is in its string).
+
+        The accepted formats for time zone offsets are +H, -H, +HH, -HH, +H:MM,
+            -H:MM, +HH:MM, and -HH:MM.
+
+
+        Params:
+            simpleString = A string formatted in the way that toSimpleString()
+                           formats dates and times.
+            tz           = The time zone to convert the given time to (no
+                           conversion occurs if null).
+
+        Throws:
+            DateTimeException if the given string is not in the ISO format or if
+            the resulting SysTime would not be valid.
+
+        Examples:
+--------------------
+assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+assert(SysTime.fromSimpleString("1998-Dec-25 02:15:00.007") ==
+       SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+assert(SysTime.fromSimpleString("0000-Jan-05 23:09:59.00002") ==
+       SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+assert(SysTime.fromSimpleString("-0004-Jan-05 00:00:02") ==
+       SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+assert(SysTime.fromSimpleString(" 2010-Jul-04 07:06:12 ") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12Z") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12-8:00") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12+8:00") ==
+       SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(480)));
+--------------------
+      +/
+    static SysTime fromSimpleString(S)(in S simpleString, immutable TimeZone tz = null)
+        if(isSomeString!(S))
+    {
+        auto dstr = to!dstring(strip(simpleString));
+
+        auto spaceIndex = dstr.indexOf(" ");
+        enforce(spaceIndex != -1, new DateTimeException(format("Invalid Simple String: %s", simpleString)));
+
+        auto found = dstr[spaceIndex + 1 .. $].find(".", "Z", "+", "-");
+        auto dateTimeStr = dstr[0 .. $ - found[0].length];
+
+        dstring fracSecStr;
+        dstring zoneStr;
+
+        if(found[1] != 0)
+        {
+            if(found[1] == 1)
+            {
+                auto foundTZ = found[0].find("Z", "+", "-");
+
+                if(foundTZ[1] != 0)
+                {
+                    fracSecStr = found[0][0 .. $ - foundTZ[0].length];
+                    zoneStr = foundTZ[0];
+                }
+                else
+                    fracSecStr = found[0];
+            }
+            else
+                zoneStr = found[0];
+        }
+
+        try
+        {
+            auto dateTime = DateTime.fromSimpleString(dateTimeStr);
+            auto fracSec = fracSecFromISOString(fracSecStr);
+            DTRebindable!(immutable TimeZone) parsedZone;
+
+            if(zoneStr.empty)
+                parsedZone = LocalTime();
+            else if(zoneStr == "Z")
+                parsedZone = UTC();
+            else
+                parsedZone = SimpleTimeZone.fromISOString(zoneStr);
+
+            auto retval = SysTime(dateTime, fracSec, parsedZone.get);
+
+            if(tz !is null)
+                retval.timezone = tz;
+
+            return retval;
+        }
+        catch(DateTimeException dte)
+            throw new DateTimeException(format("Invalid Simple String: %s", simpleString));
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assertThrown!DateTimeException(SysTime.fromSimpleString(""));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20100704000000"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20100704 000000"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20100704t000000"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20100704T000000."));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20100704T000000.0"));
+
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-07-0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-07-04 00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-07-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-07-04T00:00:00."));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-07-04T00:00:00.0"));
+
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-0400:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04t00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04T00:00:00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00."));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00.A"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00.Z"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00.00000000"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00.00000000"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00+"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00-"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00:"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00-:"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00+:"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00-1:"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00+1:"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00+1:0"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00-24.00"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-Jul-04 00:00:00+24.00"));
+
+            assertThrown!DateTimeException(SysTime.fromSimpleString("20101222T172201"));
+            assertThrown!DateTimeException(SysTime.fromSimpleString("2010-12-22T172201"));
+
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01"), SysTime(DateTime(2010, 12, 22, 17, 22, 01)));
+            assertPred!"=="(SysTime.fromSimpleString("1999-Jul-06 12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromSimpleString("-1999-Jul-06 12:30:33"), SysTime(DateTime(-1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromSimpleString("+01999-Jul-06 12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromSimpleString("1999-Jul-06 12:30:33 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromSimpleString(" 1999-Jul-06 12:30:33"), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+            assertPred!"=="(SysTime.fromSimpleString(" 1999-Jul-06 12:30:33 "), SysTime(DateTime(1999, 7, 6, 12, 30, 33)));
+
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.0"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.0000000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.0000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"hnsecs"(1)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.000001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.0000010"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"usecs"(1)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.001"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+            assertPred!"=="(SysTime.fromSimpleString("1907-Jul-07 12:12:12.0010000"), SysTime(DateTime(1907, 07, 07, 12, 12, 12), FracSec.from!"msecs"(1)));
+
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), UTC()));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), new SimpleTimeZone(480)));
+
+            assertPred!"=="(SysTime.fromSimpleString("2010-Nov-03 06:51:06.57159Z"), SysTime(DateTime(2010, 11, 3, 6, 51, 6), FracSec.from!"hnsecs"(5715900), UTC()));
+
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.23412Z"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_341_200), UTC()));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.23112-1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(2_311_200), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.45-1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(-60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.1-1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_000_000), new SimpleTimeZone(-90)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.55-8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(5_500_000), new SimpleTimeZone(-480)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.1234567+1:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(1_234_567), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.0+1"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(60)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.0000000+1:30"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(0), new SimpleTimeZone(90)));
+            assertPred!"=="(SysTime.fromSimpleString("2010-Dec-22 17:22:01.45+8:00"), SysTime(DateTime(2010, 12, 22, 17, 22, 01), FracSec.from!"hnsecs"(4_500_000), new SimpleTimeZone(480)));
+
+            //Verify Examples.
+            assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+            assert(SysTime.fromSimpleString("1998-Dec-25 02:15:00.007") == SysTime(DateTime(1998, 12, 25, 2, 15, 0), FracSec.from!"msecs"(7)));
+            assert(SysTime.fromSimpleString("0000-Jan-05 23:09:59.00002") == SysTime(DateTime(0, 1, 5, 23, 9, 59), FracSec.from!"usecs"(20)));
+            assert(SysTime.fromSimpleString("-0004-Jan-05 00:00:02") == SysTime(DateTime(-4, 1, 5, 0, 0, 2)));
+            assert(SysTime.fromSimpleString(" 2010-Jul-04 07:06:12 ") == SysTime(DateTime(2010, 7, 4, 7, 6, 12)));
+
+            assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12Z") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), UTC()));
+            assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12-8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(-480)));
+            assert(SysTime.fromSimpleString("2010-Jul-04 07:06:12+8:00") == SysTime(DateTime(2010, 7, 4, 7, 6, 12), new SimpleTimeZone(480)));
+        }
+    }
+
+
+    //TODO Add function which takes a user-specified time format and produces a SysTime
+
+    //TODO Add function which takes pretty much any time-string and produces a SysTime.
+    //     Obviously, it will be less efficient, and it probably won't manage _every_
+    //     possible date format, but a smart conversion function would be nice.
+
+
+    /++
+        Returns the SysTime farthest in the past which is representable by SysTime.
+
+        The SysTime which is returned is in UTC.
+      +/
+    @property static SysTime min() pure nothrow
+    {
+        return SysTime(long.min, UTC());
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assert(SysTime.min.year < 0);
+            assert(SysTime.min < SysTime.max);
+        }
+    }
+
+
+    /++
+        Returns the SysTime farthest in the future which is representable by SysTime.
+
+        The SysTime which is returned is in UTC.
+      +/
+    @property static SysTime max() pure nothrow
+    {
+        return SysTime(long.max, UTC());
+    }
+
+    unittest
+    {
+        version(testStdDateTime)
+        {
+            assert(SysTime.max.year > 0);
+            assert(SysTime.max > SysTime.min);
+        }
+    }
+
+
+private:
+
+    /++
+        Returns stdTime converted to SysTime's time zone.
+      +/
+    @property long adjTime() const nothrow
+    {
+        return _timezone.utcToTZ(_stdTime);
+    }
+
+
+    /++
+        Converts the given hnsecs from SysTime's time zone to std time.
+      +/
+    @property void adjTime(long adjTime) nothrow
+    {
+        _stdTime = _timezone.tzToUTC(adjTime);
+    }
+
+
+    //Commented out due to bug http://d.puremagic.com/issues/show_bug.cgi?id=5058
+    /+
+    invariant()
+    {
+        assert(_timezone.get !is null, "Invariant Failure: timezone is null. Were you foolish enough to use SysTime.init? (since timezone for SysTime.init can't be set at compile time).");
+    }
+    +/
+
+
+    long  _stdTime;
+    DTRebindable!(immutable TimeZone) _timezone;
+}
+
-
-/++
@@ -4200 +12988 @@
-
-        See_Also:
-<a href="http://en.wikipedia.org/wiki/ISO_week_date">ISO Week Date</a>
+$(WEB en.wikipedia.org/wiki/ISO_week_date, ISO Week Date)
-      +/
-    @property ubyte isoWeek() const pure nothrow
@@ -9090 +17878 @@
-
-        See_Also:
-<a href="http://en.wikipedia.org/wiki/ISO_week_date">ISO Week Date</a>
+$(WEB en.wikipedia.org/wiki/ISO_week_date, ISO Week Date)
-      +/
-    @property ubyte isoWeek() const pure nothrow
@@ -10053 +18841 @@
-    Date      _date;
-    TimeOfDay _tod;
-}
-
-
-
-/++
-    SysTime is the type used when you want to get the current time from the system
-    or if you're doing anything that involves time zones. Unlike DateTime, time
-    zone is an integral part of SysTime (though if all you care about is local
-    time, you can pretty much ignore time zones, and it will work, since it
-    defaults to using the local time zone). It holds its internal time in std time
-    (hnsecs since midnight, January 1st, 1 A.D. UTC), so it interfaces well with the
-    system time. However, that means that, unlike DateTime, it is not optimized
-    for calendar operations, and getting individual units from it such as years
-    or days is going to involve conversions and be less efficient.
-
-    Basically, if you care about calendar operations and don't necessarily care
-    about time zones, then DateTime would be the type to use. However, if what
-    you care about is the system time, then SysTime is the type to use.
-
-    $(D Clock.currTime()) will return the current time as a SysTime. If you want
-    to convert a SysTime to a Date or DateTime, simply cast it. And if you ever
-    want to convert a Date or DateTime to a SysTime, use SysTime's constructor,
-    and you can pass in the intended time zone with it (or don't pass in a
-    TimeZone, and the local time zone will be used).
-
-    If you care about using time zones other than local time or UTC, you can use
-    PosixTimeZone on Posix systems (or on Windows, if you provide the TZ Database
-    files), and you can use WindowsTimeZone on Windows systems. The time in SysTime
-    is kept internally in hnsecs from midnight, January 1st, 1 A.D. UTC. So, you
-    never get conversion errors when changing the time zone of a SysTime (since,
-    if the hnecs were kept in local time, DST would cause problems with conversions).
-    LocalTime is the TimeZone class which represents the local time, and UTC is the
-    TimeZone class which represents UTC. SysTime uses LocalTime if no TimeZone is
-    provided. For more details on time zones, look at the documentation for
-    TimeZone, PosixTimeZone, and WindowsTimeZone.
-
-    SysTime's range is from approximately 29,000 B.C. to 29,000 A.D.
-  +/
-struct SysTime
-{
-public:
-
-    /++
-        Params:
-            dateTime = The DateTime to use to set this SysTime's internal std
-                       time. As DateTime has no concept of time zone, tz is used
-                       as its time zone.
-            tz       = The TimeZone to use for this SysTime. If null, LocalTime
-                       will be used. The given DateTime is assumed to be in the
-                       given time zone.
-      +/
-    this(in DateTime dateTime, immutable TimeZone tz = null) nothrow
-    {
-        try
-            this(dateTime, FracSec.from!"hnsecs"(0), tz);
-        catch(Exception e)
-            assert(0, "FracSec's constructor threw when it shouldn't have.");
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(DateTime.init, UTC())._stdTime, 0);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 30, 33), UTC())._stdTime, 450_330_000_000L);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 30, 33), UTC())._stdTime, -413_670_000_000L);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), UTC())._stdTime, 0);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 1), UTC())._stdTime, 10_000_000L);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), UTC())._stdTime, -10_000_000L);
-
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(-60)).stdTime, 36_000_000_000L);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(0)).stdTime, 0);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), new SimpleTimeZone(60)).stdTime, -36_000_000_000L);
-        }
-    }
-
-
-    /++
-        Params:
-            dateTime = The DateTime to use to set this SysTime's internal std time.
-                       As DateTime has no concept of time zone, tz is used as its
-                       time zone.
-            fsec     = The fractional seconds portion of the time.
-            tz       = The TimeZone to use for this SysTime. If null, LocalTime will
-                       be used. The given DateTime is assumed to be in the given
-                       time zone.
-      +/
-    this(in DateTime dateTime, in FracSec fsec, immutable TimeZone tz = null) nothrow
-    {
-        if(tz is null)
-            _timezone = LocalTime();
-        else
-            _timezone = tz;
-
-        try
-        {
-            immutable dateDiff = (dateTime.date - Date(1, 1, 1)).total!"hnsecs";
-            immutable todDiff = (dateTime.timeOfDay - TimeOfDay(0, 0, 0)).total!"hnsecs";
-
-            immutable adjustedTime = dateDiff + todDiff + fsec.hnsecs;
-            immutable standardTime = _timezone.tzToUTC(adjustedTime);
-
-            this(standardTime, _timezone.get);
-        }
-        catch(Exception e)
-            assert(0, "Date, TimeOfDay, or DateTime's constructor threw when it shouldn't have.");
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(DateTime.init, FracSec.init, UTC())._stdTime, 0);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 30, 33), FracSec.init, UTC())._stdTime, 450_330_000_000L);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 12, 30, 33), FracSec.init, UTC())._stdTime, -413_670_000_000L);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"msecs"(1), UTC())._stdTime, 10_000L);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC())._stdTime, -10_000L);
-
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).stdTime, -1);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1), UTC()).stdTime, -9_999_999);
-            assertPred!"=="(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0), UTC()).stdTime, -10_000_000);
-        }
-    }
-
-
-    /++
-        Params:
-            date = The Date to use to set this SysTime's internal std time.
-                   As Date has no concept of time zone, tz is used as its
-                   time zone.
-            tz   = The TimeZone to use for this SysTime. If null, LocalTime will
-                   be used. The given Date is assumed to be in the given time zone.
-      +/
-    this(in Date date, immutable TimeZone tz = null) nothrow
-    {
-        if(tz is null)
-            _timezone = LocalTime();
-        else
-            _timezone = tz;
-
-        try
-        {
-            immutable adjustedTime = (date - Date(1, 1, 1)).total!"hnsecs";
-            immutable standardTime = _timezone.tzToUTC(adjustedTime);
-
-            this(standardTime, _timezone.get);
-        }
-        catch(Exception e)
-            assert(0, "Date's constructor through when it shouldn't have");
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(Date.init, UTC())._stdTime, 0);
-            assertPred!"=="(SysTime(Date(1, 1, 1), UTC())._stdTime, 0);
-            assertPred!"=="(SysTime(Date(1, 1, 2), UTC())._stdTime, 864000000000);
-            assertPred!"=="(SysTime(Date(0, 12, 31), UTC())._stdTime, -864000000000);
-        }
-    }
-
-
-    /++
-        Note:
-            Whereas the other constructors take in the given date/time, assume
-            that it's in the given time zone, and convert it to hnsecs in UTC
-            since midnight, January 1st, 1 A.D. UTC - i.e. std time - this constructor
-            takes a std time, which is specifically already in UTC, so no conversion
-            takes place. Of course, the various getter properties and functions
-            will use the given time zone's conversion function to convert the
-            results to that time zone, but no conversion of the arguments to
-            this constructor takes place.
-
-        Params:
-            stdTime = The number of hnsecs since midnight, January 1st, 1 A.D. UTC.
-            tz    = The TimeZone to use for this SysTime. If null, LocalTime will be used.
-      +/
-    this(long stdTime, immutable TimeZone tz = null) pure nothrow
-    {
-        _stdTime = stdTime;
-
-        if(tz is null)
-            _timezone = LocalTime();
-        else
-            _timezone = tz;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0)._stdTime, 0);
-        }
-    }
-
-
-    /++
-        Params:
-            rhs = The SysTime to assign to this one.
-      +/
-    ref SysTime opAssign(const ref SysTime rhs) pure nothrow
-    {
-        _stdTime = rhs._stdTime;
-        _timezone = rhs._timezone.get;
-
-        return this;
-    }
-
-
-    /++
-        Params:
-            rhs = The SysTime to assign to this one.
-      +/
-    ref SysTime opAssign(SysTime rhs) pure nothrow
-    {
-        _stdTime = rhs._stdTime;
-        _timezone = rhs._timezone.get;
-
-        return this;
-    }
-
-
-    /++
-        Checks for equality between this SysTime and the given
-        SysTime.
-
-        Note that the time zone is ignored. Only the internal
-        std times (which are in UTC) are compared.
-     +/
-    bool opEquals(const ref SysTime rhs) const pure nothrow
-    {
-        return _stdTime == rhs._stdTime;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            auto a = SysTime(DateTime.init, UTC());
-            auto b = SysTime(0, UTC());
-            assert(a == b);
-            assertPred!"=="(a, b);
-            assertPred!"=="(SysTime(DateTime.init, UTC()), SysTime(0, UTC()));
-            assertPred!"=="(SysTime(Date.init, UTC()), SysTime(0, UTC()));
-            assertPred!"=="(SysTime(0), SysTime(0));
-
-            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
-            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
-            assertPred!"=="(SysTime(Date(1, 7, 1)), SysTime(Date(1, 7, 1)));
-            assertPred!"=="(SysTime(Date(1, 1, 6)), SysTime(Date(1, 1, 6)));
-
-            assertPred!"=="(SysTime(Date(1999, 7, 1)), SysTime(Date(1999, 7, 1)));
-            assertPred!"=="(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 6)));
-
-            assertPred!"=="(SysTime(Date(1, 7, 6)), SysTime(Date(1, 7, 6)));
-
-            assertPred!"=="(SysTime(DateTime(1999, 1, 1, 0, 0, 0)), SysTime(Date(1999, 1, 1)));
-            assertPred!"=="(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 0, 0, 0)));
-
-            assertPred!"!="(SysTime(DateTime(1999, 1, 1, 11, 30, 20)), SysTime(Date(1999, 1, 1)));
-            assertPred!"!="(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 11, 30, 20)));
-
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))));
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))));
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))));
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
-
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))));
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))));
-            assertPred!"=="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
-                        SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
-
-            {
-                auto sysUTC = SysTime(Date(1999, 1, 1));
-                sysUTC.timezone = UTC();
-
-                auto sysLocal = SysTime(Date(1999, 1, 1));
-                sysUTC.timezone = LocalTime();
-
-                assertPred!"=="(sysUTC, sysLocal);
-                assertPred!"=="(sysLocal, sysUTC);
-
-                if(!localTimeIsUTC)
-                {
-                    assertPred!"!="(SysTime(Date(1999, 1, 1), UTC()), SysTime(Date(1999, 1, 1), LocalTime()));
-                    assertPred!"!="(SysTime(Date(1999, 7, 1), LocalTime()), SysTime(Date(1999, 7, 1), UTC()));
-                }
-            }
-
-            {
-                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
-                sysUTC.timezone = UTC();
-
-                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
-                sysSimple.timezone = new SimpleTimeZone(-360);
-
-                assertPred!"=="(sysUTC, sysSimple);
-                assertPred!"=="(sysSimple, sysUTC);
-
-                assertPred!"!="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()),
-                               SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone));
-                assertPred!"!="(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone),
-                               SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()));
-            }
-
-            {
-                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC());
-                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), new SimpleTimeZone(240));
-
-                assertPred!"!="(sysUTC, sysSimple);
-                assertPred!"!="(sysSimple, sysUTC);
-
-                sysUTC = SysTime(DateTime(Date(1999, 7, 5), TimeOfDay(20, 0, 0)), UTC());
-
-                assertPred!"=="(sysUTC, sysSimple);
-                assertPred!"=="(sysSimple, sysUTC);
-            }
-
-            auto st = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            static assert(__traits(compiles, st == st));
-            static assert(__traits(compiles, st == cst));
-            //static assert(__traits(compiles, st == ist));
-            static assert(__traits(compiles, cst == st));
-            static assert(__traits(compiles, cst == cst));
-            //static assert(__traits(compiles, cst == ist));
-            //static assert(__traits(compiles, ist == st));
-            //static assert(__traits(compiles, ist == cst));
-            //static assert(__traits(compiles, ist == ist));
-        }
-    }
-
-
-    /++
-        Compares this SysTime with the given SysTime.
-
-        Time zone is irrelevant to comparing SysTimes.
-
-        Returns:
-            $(TABLE
-            $(TR $(TD this &lt; rhs) $(TD &lt; 0))
-            $(TR $(TD this == rhs) $(TD 0))
-            $(TR $(TD this &gt; rhs) $(TD &gt; 0))
-            )
-     +/
-    int opCmp(in SysTime rhs) const pure nothrow
-    {
-        if(_stdTime < rhs._stdTime)
-            return -1;
-        if(_stdTime > rhs._stdTime)
-            return 1;
-
-        return 0;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            assertPred!("opCmp", "==")(SysTime(DateTime.init, UTC()), SysTime(0));
-            assertPred!("opCmp", "==")(SysTime(Date.init, UTC()), SysTime(0));
-
-            assertPred!("opCmp", "==")(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
-            assertPred!("opCmp", "==")(SysTime(Date(1999, 1, 1)), SysTime(Date(1999, 1, 1)));
-            assertPred!("opCmp", "==")(SysTime(Date(1, 7, 1)), SysTime(Date(1, 7, 1)));
-            assertPred!("opCmp", "==")(SysTime(Date(1, 1, 6)), SysTime(Date(1, 1, 6)));
-
-            assertPred!("opCmp", "==")(SysTime(Date(1999, 7, 1)), SysTime(Date(1999, 7, 1)));
-            assertPred!("opCmp", "==")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 6)));
-
-            assertPred!("opCmp", "==")(SysTime(Date(1, 7, 6)), SysTime(Date(1, 7, 6)));
-
-            assertPred!("opCmp", ">")(SysTime(DateTime(1999, 1, 1, 11, 30, 20)), SysTime(Date(1999, 1, 1)));
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 1, 1)), SysTime(DateTime(1999, 1, 1, 11, 30, 20)));
-
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(2000, 7, 6)));
-            assertPred!("opCmp", ">")(SysTime(Date(2000, 7, 6)), SysTime(Date(1999, 7, 6)));
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 8, 6)));
-            assertPred!("opCmp", ">")(SysTime(Date(1999, 8, 6)), SysTime(Date(1999, 7, 6)));
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 6)), SysTime(Date(1999, 7, 7)));
-            assertPred!("opCmp", ">")(SysTime(Date(1999, 7, 7)), SysTime(Date(1999, 7, 6)));
-
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 8, 7)), SysTime(Date(2000, 7, 6)));
-            assertPred!("opCmp", ">")(SysTime(Date(2000, 8, 6)), SysTime(Date(1999, 7, 7)));
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 7)), SysTime(Date(2000, 7, 6)));
-            assertPred!("opCmp", ">")(SysTime(Date(2000, 7, 6)), SysTime(Date(1999, 7, 7)));
-            assertPred!("opCmp", "<")(SysTime(Date(1999, 7, 7)), SysTime(Date(1999, 8, 6)));
-            assertPred!("opCmp", ">")(SysTime(Date(1999, 8, 6)), SysTime(Date(1999, 7, 7)));
-
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0)))),
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
-
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))),
-                                       SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                     SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 31, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))),
-                                      SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))));
-
-            //Test B.C.
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "==")(SysTime(DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33))),
-                                       SysTime(DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
-
-            //Test Both
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))));
-
-            assertPred!("opCmp", "<")(SysTime(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(1999, 6, 6), TimeOfDay(12, 30, 33))));
-            assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 6, 8), TimeOfDay(12, 30, 33))),
-                                      SysTime(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))));
-
-            {
-                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
-                sysUTC.timezone = UTC();
-
-                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
-                sysSimple.timezone = new SimpleTimeZone(-360);
-
-                assertPred!("opCmp", "==")(sysUTC, sysSimple);
-                assertPred!("opCmp", "==")(sysSimple, sysUTC);
-
-                assertPred!("opCmp", "<")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()),
-                                         SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone));
-                assertPred!("opCmp", ">")(SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), sysSimple.timezone),
-                                         SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC()));
-            }
-
-            {
-                auto sysUTC = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), UTC());
-                auto sysSimple = SysTime(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), new SimpleTimeZone(240));
-
-                assertPred!("opCmp", ">")(sysUTC, sysSimple);
-                assertPred!("opCmp", "<")(sysSimple, sysUTC);
-
-                sysUTC = SysTime(DateTime(Date(1999, 7, 5), TimeOfDay(20, 0, 0)), UTC());
-
-                assertPred!("opCmp", "==")(sysUTC, sysSimple);
-                assertPred!("opCmp", "==")(sysSimple, sysUTC);
-            }
-
-            auto st = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 33, 30));
-            static assert(__traits(compiles, st.opCmp(st)));
-            static assert(__traits(compiles, st.opCmp(cst)));
-            //static assert(__traits(compiles, st.opCmp(ist)));
-            static assert(__traits(compiles, cst.opCmp(st)));
-            static assert(__traits(compiles, cst.opCmp(cst)));
-            //static assert(__traits(compiles, cst.opCmp(ist)));
-            //static assert(__traits(compiles, ist.opCmp(st)));
-            //static assert(__traits(compiles, ist.opCmp(cst)));
-            //static assert(__traits(compiles, ist.opCmp(ist)));
-        }
-    }
-
-
-    /++
-        Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
-        are B.C.
-     +/
-    @property short year() const nothrow
-    {
-        return (cast(Date)this).year;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).year, 1);
-            assertPred!"=="(SysTime(1, UTC()).year, 1);
-            assertPred!"=="(SysTime(-1, UTC()).year, 0);
-            assertPred!"=="(SysTime(DateTime(12, 1, 1, 0, 0, 0)).year, 12);
-            assertPred!"=="(SysTime(DateTime(-12, 1, 1, 0, 0, 0)).year, -12);
-            assertPred!"=="(SysTime(Date(1999, 7, 6)).year, 1999);
-            assertPred!"=="(SysTime(Date(-1999, 7, 6)).year, -1999);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.year));
-            //static assert(__traits(compiles, ist.year));
-        }
-    }
-
-
-    /++
-        Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
-        are B.C.
-
-        Params:
-            year = The year to set this SysTime's year to.
-
-        Throws:
-            DateTimeException if the new year is not a leap year and the resulting
-            date would be on February 29th.
-
-        Examples:
---------------------
-assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).year == 1999);
-assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).year == 2010);
-assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).year == -7);
---------------------
-     +/
-    @property void year(int year)
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.year = year;
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
-
-        adjTime = newDaysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testST(SysTime st, int year, in SysTime expected, size_t line = __LINE__)
-            {
-                st.year = year;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1999, SysTime(Date(1999, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 0, SysTime(Date(0, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), -1999, SysTime(Date(-1999, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), -1999, SysTime(DateTime(-1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 1999, SysTime(Date(1999, 1, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 0, SysTime(Date(0, 1, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), -1999, SysTime(Date(-1999, 1, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), -1999, SysTime(DateTime(-1999, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(12, 7, 2)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(5, 7, 2)));
-            testST(SysTime(Date(0, 7, 2)), 999, SysTime(Date(999, 7, 2)));
-            testST(SysTime(Date(-1202, 7, 2)), 2300, SysTime(Date(2300, 7, 2)));
-
-            testST(SysTime(Date(1, 7, 2)), -12, SysTime(Date(-12, 7, 2)));
-            testST(SysTime(Date(5007, 7, 2)), -5, SysTime(Date(-5, 7, 2)));
-            testST(SysTime(Date(0, 7, 2)), -999, SysTime(Date(-999, 7, 2)));
-            testST(SysTime(Date(-1202, 7, 2)), -2300, SysTime(Date(-2300, 7, 2)));
-
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -1, SysTime(DateTime(-1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(999, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(2010, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -507, SysTime(DateTime(-507, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(2300, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(12, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -1, SysTime(DateTime(-1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(999, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(2010, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(5, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 0, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), -507, SysTime(DateTime(-507, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(2300, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(12, 1, 1, 0, 0, 0), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.year = 7));
-            //static assert(!__traits(compiles, ist.year = 7));
-
-            //Verify Examples.
-            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).year == 1999);
-            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).year == 2010);
-            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).year == -7);
-        }
-    }
-
-
-    /++
-        Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
-
-        Throws:
-            DateTimeException if $(D isAD) is true.
-
-        Examples:
---------------------
-assert(SysTime(DateTime(0, 1, 1, 12, 30, 33)).yearBC == 1);
-assert(SysTime(DateTime(-1, 1, 1, 10, 7, 2)).yearBC == 2);
-assert(SysTime(DateTime(-100, 1, 1, 4, 59, 0)).yearBC == 101);
---------------------
-     +/
-    @property ushort yearBC() const
-    {
-        return (cast(Date)this).yearBC;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(Date(1, 1, 1), UTC())));
-            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(0, UTC())));
-            assertThrown!DateTimeException((in SysTime st){st.yearBC;}(SysTime(1, UTC())));
-
-            assertPred!"=="(SysTime(-1, UTC()).yearBC, 1);
-            assertPred!"=="(SysTime(DateTime(-12, 1, 1, 0, 0, 0)).yearBC, 13);
-
-            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, st.year = 12));
-            static assert(!__traits(compiles, cst.year = 12));
-            //static assert(!__traits(compiles, ist.year = 12));
-
-            //Verify Examples.
-            assert(SysTime(DateTime(0, 1, 1, 12, 30, 33)).yearBC == 1);
-            assert(SysTime(DateTime(-1, 1, 1, 10, 7, 2)).yearBC == 2);
-            assert(SysTime(DateTime(-100, 1, 1, 4, 59, 0)).yearBC == 101);
-        }
-    }
-
-
-    /++
-        Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
-
-        Params:
-            year = The year B.C. to set this SysTime's year to.
-
-        Throws:
-            DateTimeException if a non-positive value is given.
-
-        Examples:
---------------------
-auto st = SysTime(DateTime(2010, 1, 1, 7, 30, 0));
-st.yearBC = 1;
-assert(st == SysTime(DateTime(0, 1, 1, 7, 30, 0)));
-
-st.yearBC = 10;
-assert(st == SysTime(DateTime(-9, 1, 1, 7, 30, 0)));
---------------------
-     +/
-    @property void yearBC(int year)
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.yearBC = year;
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
-
-        adjTime = newDaysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, int year)
-            {
-                st.yearBC = year;
-            }
-
-            static void testST(SysTime st, int year, in SysTime expected, size_t line = __LINE__)
-            {
-                st.yearBC = year;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 0));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), -1));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), -1202));
-
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1999, SysTime(Date(-1998, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1, SysTime(Date(0, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1999, SysTime(DateTime(-1998, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(-11, 7, 2)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(-4, 7, 2)));
-            testST(SysTime(Date(0, 7, 2)), 999, SysTime(Date(-998, 7, 2)));
-            testST(SysTime(Date(-1202, 7, 2)), 2300, SysTime(Date(-2299, 7, 2)));
-
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(-998, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(1, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(-2009, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(-2299, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(5007, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(-5006, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 12, SysTime(DateTime(-11, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 1, SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 999, SysTime(DateTime(-998, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(0, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2010, SysTime(DateTime(-2009, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5, SysTime(DateTime(-4, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 2300, SysTime(DateTime(-2299, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-            testST(SysTime(DateTime(-1202, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)), 5007, SysTime(DateTime(-5006, 7, 2, 1, 3, 2), FracSec.from!"hnsecs"(5007)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(-11, 1, 1, 0, 0, 0), UTC()));
-
-            {
-                auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-                const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-                //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-                static assert(__traits(compiles, st.yearBC = 12));
-                static assert(!__traits(compiles, cst.yearBC = 12));
-                //static assert(!__traits(compiles, ist.yearBC = 12));
-            }
-
-            //Verify Examples.
-            {
-                auto st = SysTime(DateTime(2010, 1, 1, 7, 30, 0));
-                st.yearBC = 1;
-                assert(st == SysTime(DateTime(0, 1, 1, 7, 30, 0)));
-
-                st.yearBC = 10;
-                assert(st == SysTime(DateTime(-9, 1, 1, 7, 30, 0)));
-            }
-        }
-    }
-
-
-    /++
-        Month of a Gregorian Year.
-
-        Examples:
---------------------
-assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).month == 7);
-assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).month == 10);
-assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).month == 4);
---------------------
-     +/
-    @property Month month() const nothrow
-    {
-        return (cast(Date)this).month;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).month, 1);
-            assertPred!"=="(SysTime(1, UTC()).month, 1);
-            assertPred!"=="(SysTime(-1, UTC()).month, 12);
-            assertPred!"=="(SysTime(DateTime(1, 12, 1, 0, 0, 0)).month, 12);
-            assertPred!"=="(SysTime(DateTime(0, 12, 1, 0, 0, 0)).month, 12);
-            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)).month, 7);
-            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 12, 30, 33)).month, 7);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.month));
-            //static assert(__traits(compiles, ist.month));
-
-            //Verify Examples.
-            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).month == 7);
-            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).month == 10);
-            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).month == 4);
-        }
-    }
-
-
-    /++
-        Month of a Gregorian Year.
-
-        Params:
-            month = The month to set this SysTime's month to.
-
-        Throws:
-            DateTimeException if the given month is not a valid month.
-     +/
-    @property void month(Month month)
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.month = month;
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
-
-        adjTime = newDaysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, Month month)
-            {
-                st.month = month;
-            }
-
-            static void testST(SysTime st, Month month, in SysTime expected, size_t line = __LINE__)
-            {
-                st.month = month;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 1, 12, 30, 33)), cast(Month)0));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 1, 12, 30, 33)), cast(Month)13));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 1, 29, 12, 30, 33)), cast(Month)2));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(1, 7, 31, 12, 30, 33)), cast(Month)6));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(DateTime(4, 7, 30, 12, 30, 33)), cast(Month)2));
-
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)1, SysTime(Date(1, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)7, SysTime(Date(1, 7, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), cast(Month)12, SysTime(Date(1, 12, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)7, SysTime(DateTime(1, 7, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)1, SysTime(Date(0, 1, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)7, SysTime(Date(0, 7, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), cast(Month)12, SysTime(Date(0, 12, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)7, SysTime(DateTime(0, 7, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), cast(Month)12, SysTime(Date(1, 12, 2)));
-            testST(SysTime(Date(5007, 7, 2)), cast(Month)5, SysTime(Date(5007, 5, 2)));
-            testST(SysTime(Date(0, 7, 2)), cast(Month)7, SysTime(Date(0, 7, 2)));
-            testST(SysTime(Date(-1202, 7, 2)), cast(Month)1, SysTime(Date(-1202, 1, 2)));
-
-            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)), cast(Month)7, SysTime(DateTime(1, 7, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)));
-            testST(SysTime(DateTime(1, 11, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)), cast(Month)1, SysTime(DateTime(1, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)));
-            testST(SysTime(DateTime(1, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)), cast(Month)2, SysTime(DateTime(1, 2, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)));
-            testST(SysTime(DateTime(1, 7, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)),cast(Month) 6, SysTime(DateTime(1, 6, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)));
-            testST(SysTime(DateTime(4, 7, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)2, SysTime(DateTime(4, 2, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(4, 7, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)8, SysTime(DateTime(4, 8, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)));
-
-            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)), cast(Month)12, SysTime(DateTime(1207, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)));
-            testST(SysTime(DateTime(1207, 12, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)), cast(Month)7, SysTime(DateTime(1207, 7, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)));
-            testST(SysTime(DateTime(1207, 11, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)), cast(Month)1, SysTime(DateTime(1207, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(1207, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)), cast(Month)2, SysTime(DateTime(1207, 2, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)));
-            testST(SysTime(DateTime(1207, 7, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)), cast(Month)6, SysTime(DateTime(1207, 6, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)));
-
-            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)), cast(Month)12, SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)), cast(Month)7, SysTime(DateTime(0, 7, 29, 9, 13, 2), FracSec.from!"hnsecs"(2)));
-            testST(SysTime(DateTime(0, 11, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)), cast(Month)1, SysTime(DateTime(0, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(3)));
-            testST(SysTime(DateTime(0, 1, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)), cast(Month)2, SysTime(DateTime(0, 2, 28, 10, 13, 2), FracSec.from!"hnsecs"(4)));
-            testST(SysTime(DateTime(0, 7, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)), cast(Month)6, SysTime(DateTime(0, 6, 28, 10, 13, 2), FracSec.from!"hnsecs"(5)));
-
-            testST(SysTime(DateTime(0, 12, 30, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)11, SysTime(DateTime(0, 11, 30, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(-1, 7, 28, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)2, SysTime(DateTime(-1, 2, 28, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 7, 29, 0, 0, 0), FracSec.from!"hnsecs"(1)), cast(Month)2, SysTime(DateTime(0, 2, 29, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 7, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)2, SysTime(DateTime(0, 2, 29, 10, 13, 2), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(0, 7, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)), cast(Month)8, SysTime(DateTime(0, 8, 31, 10, 13, 2), FracSec.from!"hnsecs"(6)));
-
-            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)), cast(Month)12, SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)), cast(Month)12, SysTime(DateTime(-9999, 12, 29, 9, 12, 2), FracSec.from!"hnsecs"(11)));
-            testST(SysTime(DateTime(-9999, 12, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)), cast(Month)7, SysTime(DateTime(-9999, 7, 29, 9, 12, 3), FracSec.from!"hnsecs"(10)));
-            testST(SysTime(DateTime(-9999, 11, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)), cast(Month)1, SysTime(DateTime(-9999, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(-9999, 1, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)), cast(Month)2, SysTime(DateTime(-9999, 2, 28, 10, 12, 3), FracSec.from!"hnsecs"(8)));
-            testST(SysTime(DateTime(-9999, 7, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)), cast(Month)6, SysTime(DateTime(-9999, 6, 28, 10, 12, 3), FracSec.from!"hnsecs"(7)));
-
-            testST(SysTime(0, UTC()), cast(Month)12, SysTime(DateTime(1, 12, 1, 0, 0, 0), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.month = 12));
-            //static assert(!__traits(compiles, ist.month = 12));
-        }
-    }
-
-
-    /++
-        Day of a Gregorian Month.
-
-        Examples:
---------------------
-assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).day == 6);
-assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).day == 4);
-assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).day == 5);
---------------------
-     +/
-    @property ubyte day() const nothrow
-    {
-        return (cast(Date)this).day;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).day, 1);
-            assertPred!"=="(SysTime(1, UTC()).day, 1);
-            assertPred!"=="(SysTime(-1, UTC()).day, 31);
-            assertPred!"=="(SysTime(DateTime(50, 2, 4)).day, 4);
-            assertPred!"=="(SysTime(DateTime(50, 2, 4, 0, 0, 1)).day, 4);
-            assertPred!"=="(SysTime(DateTime(1999, 7, 6)).day, 6);
-            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 0, 0, 0)).day, 6);
-            assertPred!"=="(SysTime(DateTime(1999, 7, 6, 12, 30, 33)).day, 6);
-            assertPred!"=="(SysTime(DateTime(-50, 2, 4)).day, 4);
-            assertPred!"=="(SysTime(DateTime(-50, 2, 4, 0, 0, 1)).day, 4);
-            assertPred!"=="(SysTime(Date(-1999, 7, 6)).day, 6);
-            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 0, 0, 0)).day, 6);
-            assertPred!"=="(SysTime(DateTime(-1999, 7, 6, 12, 30, 33)).day, 6);
-
-            assertPred!"=="(SysTime(DateTime(1, 1, 12, 0, 0, 0)).day, 12);
-            assertPred!"=="(SysTime(DateTime(0, 1, 12, 0, 0, 0)).day, 12);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.day));
-            //static assert(__traits(compiles, ist.day));
-
-            //Verify Examples.
-            assert(SysTime(DateTime(1999, 7, 6, 9, 7, 5)).day == 6);
-            assert(SysTime(DateTime(2010, 10, 4, 0, 0, 30)).day == 4);
-            assert(SysTime(DateTime(-7, 4, 5, 7, 45, 2)).day == 5);
-        }
-    }
-
-
-    /++
-        Day of a Gregorian Month.
-
-        Params:
-            day = The day of the month to set this SysTime's day to.
-
-        Throws:
-            DateTimeException if the given day is not a valid day of the current
-            month.
-     +/
-    @property void day(int day)
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.day = day;
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(date.dayOfGregorianCal - 1);
-
-        adjTime = newDaysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, int day)
-            {
-                st.day = day;
-            }
-
-            static void testST(SysTime st, int day, in SysTime expected, size_t line = __LINE__)
-            {
-                st.day = day;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            //Test A.D.
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 0));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 2, 1)), 29));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(4, 2, 1)), 30));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 3, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 4, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 5, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 6, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 7, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 8, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 9, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 10, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 11, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 12, 1)), 32));
-
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 1, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 2, 1)), 28));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(4, 2, 1)), 29));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 3, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 4, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 5, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 6, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 7, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 8, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 9, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 10, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 11, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(1, 12, 1)), 31));
-
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 1, SysTime(Date(1, 1, 1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 7, SysTime(Date(1, 1, 7)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0)), 12, SysTime(Date(1, 1, 12)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 7, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 12, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(Date(1, 7, 12)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(Date(5007, 7, 5)));
-
-            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 29, SysTime(DateTime(1, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 29, SysTime(DateTime(999, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(900_000)));
-
-            //Test B.C.
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 0));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 2, 1)), 29));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(0, 2, 1)), 30));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 3, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 4, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 5, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 6, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 7, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 8, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 9, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 10, 1)), 32));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 11, 1)), 31));
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 12, 1)), 32));
-
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 1, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 2, 1)), 28));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(0, 2, 1)), 29));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 3, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 4, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 5, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 6, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 7, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 8, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 9, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 10, 1)), 31));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 11, 1)), 30));
-            assertNotThrown!DateTimeException(testSTInvalid(SysTime(Date(-1, 12, 1)), 31));
-
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 1, SysTime(Date(0, 1, 1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 7, SysTime(Date(0, 1, 7)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0)), 12, SysTime(Date(0, 1, 12)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 7, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 12, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(0, 7, 2)), 7, SysTime(Date(0, 7, 7)));
-            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(Date(-1202, 7, 1)));
-
-            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 29, SysTime(DateTime(0, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 6, 12, 22, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 5, 12, 22, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 29, SysTime(DateTime(-1, 12, 29, 12, 22, 17), FracSec.from!"hnsecs"(900_000)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 12, 0, 0, 0), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.day = 27));
-            //static assert(!__traits(compiles, ist.day = 27));
-        }
-    }
-
-
-    /++
-        Hours past midnight.
-     +/
-    @property ubyte hour() const nothrow
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        return cast(ubyte)getUnitsFromHNSecs!"hours"(hnsecs);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).hour, 0);
-            assertPred!"=="(SysTime(1, UTC()).hour, 0);
-            assertPred!"=="(SysTime(-1, UTC()).hour, 23);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 12, 0, 0)).hour, 12);
-            assertPred!"=="(SysTime(DateTime(0, 1, 1, 12, 0, 0)).hour, 12);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.hour));
-            //static assert(__traits(compiles, ist.hour));
-        }
-    }
-
-
-    /++
-        Hours past midnight.
-
-        Params:
-            hour = The hours to set this SysTime's hour to.
-
-        Throws:
-            DateTimeException if the given hour are not a valid hour of the day.
-     +/
-    @property void hour(int hour)
-    {
-        enforceValid!"hours"(hour);
-
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
-        immutable daysHNSecs = convert!("days", "hnsecs")(days);
-        immutable negative = hnsecs < 0;
-
-        if(negative)
-            hnsecs += convert!("hours", "hnsecs")(24);
-
-        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
-        hnsecs += convert!("hours", "hnsecs")(hour);
-
-        if(negative)
-            hnsecs -= convert!("hours", "hnsecs")(24);
-
-        adjTime = daysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, int hour)
-            {
-                st.hour = hour;
-            }
-
-            static void testST(SysTime st, int hour, in SysTime expected, size_t line = __LINE__)
-            {
-                st.hour = hour;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 24));
-
-            //Test A.D.
-            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 1, 0, 0)));
-            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 7, 0, 0)));
-            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 1, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 7, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 1, 59, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 7, 59, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 12, 59, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 1, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 7, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 12, 59, 59), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 12, 0, 0)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 5, 0, 0)));
-
-            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(900_000)));
-
-            //Test B.C.
-            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 1, 0, 0)));
-            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 7, 0, 0)));
-            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 12, 0, 0)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 1, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 7, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 12, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 1, 59, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 7, 59, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 12, 59, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 1, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 7, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 12, 59, 59), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 7, 0, 0)));
-            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 1, 0, 0)));
-
-            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 6, 22, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 1, 22, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 1, 22, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 5, 22, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 1, 22, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 23, 22, 17), FracSec.from!"hnsecs"(900_000)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 12, 0, 0), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.hour = 27));
-            //static assert(!__traits(compiles, ist.hour = 27));
-        }
-    }
-
-
-    /++
-        Minutes past the current hour.
-     +/
-    @property ubyte minute() const nothrow
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
-
-        return cast(ubyte)getUnitsFromHNSecs!"minutes"(hnsecs);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).minute, 0);
-            assertPred!"=="(SysTime(1, UTC()).minute, 0);
-            assertPred!"=="(SysTime(-1, UTC()).minute, 59);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 30, 0)).minute, 30);
-            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 30, 0)).minute, 30);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.minute));
-            //static assert(__traits(compiles, ist.minute));
-        }
-    }
-
-
-    /++
-        Minutes past the current hour.
-
-        Params:
-            minutes = The minute to set this SysTime's minute to.
-
-        Throws:
-            DateTimeException if the given minute are not a valid minute of an
-            hour.
-     +/
-    @property void minute(int minute)
-    {
-        enforceValid!"minutes"(minute);
-
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
-        immutable daysHNSecs = convert!("days", "hnsecs")(days);
-        immutable negative = hnsecs < 0;
-
-        if(negative)
-            hnsecs += convert!("hours", "hnsecs")(24);
-
-        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
-        hnsecs = removeUnitsFromHNSecs!"minutes"(hnsecs);
-
-        hnsecs += convert!("hours", "hnsecs")(hour);
-        hnsecs += convert!("minutes", "hnsecs")(minute);
-
-        if(negative)
-            hnsecs -= convert!("hours", "hnsecs")(24);
-
-        adjTime = daysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, int minute)
-            {
-                st.minute = minute;
-            }
-
-            static void testST(SysTime st, int minute, in SysTime expected, size_t line = __LINE__)
-            {
-                st.minute = minute;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 60));
-
-            //Test A.D.
-            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 1, 0)));
-            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 7, 0)));
-            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 1, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 7, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 1, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 7, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 12, 59)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 1, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 7, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 12, 59), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 12, 0)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 5, 0)));
-
-            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(900_000)));
-
-            //Test B.C.
-            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 1, 0)));
-            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 7, 0)));
-            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 12, 0)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 1, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 7, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 12, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 1, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 7, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 12, 59)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 1, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 7, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 12, 59), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 7, 0)));
-            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 1, 0)));
-
-            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 6, 17), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 1, 17), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 1, 17), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 5, 17), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 1, 17), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 23, 17), FracSec.from!"hnsecs"(900_000)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 12, 0), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.minute = 27));
-            //static assert(!__traits(compiles, ist.minute = 27));
-        }
-    }
-
-
-    /++
-        Seconds past the current minute.
-     +/
-    @property ubyte second() const nothrow
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        hnsecs = removeUnitsFromHNSecs!"hours"(hnsecs);
-        hnsecs = removeUnitsFromHNSecs!"minutes"(hnsecs);
-
-        return cast(ubyte)getUnitsFromHNSecs!"seconds"(hnsecs);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).second, 0);
-            assertPred!"=="(SysTime(1, UTC()).second, 0);
-            assertPred!"=="(SysTime(-1, UTC()).second, 59);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33)).second, 33);
-            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 0, 33)).second, 33);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.second));
-            //static assert(__traits(compiles, ist.second));
-        }
-    }
-
-
-    /++
-        Seconds past the current minute.
-
-        Params
-            second = The second to set this SysTime's second to.
-
-        Throws:
-            DateTimeException if the given second are not a valid second of a minute.
-     +/
-    @property void second(int second)
-    {
-        enforceValid!"seconds"(second);
-
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
-        immutable daysHNSecs = convert!("days", "hnsecs")(days);
-        immutable negative = hnsecs < 0;
-
-        if(negative)
-            hnsecs += convert!("hours", "hnsecs")(24);
-
-        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
-        immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
-        hnsecs = removeUnitsFromHNSecs!"seconds"(hnsecs);
-
-        hnsecs += convert!("hours", "hnsecs")(hour);
-        hnsecs += convert!("minutes", "hnsecs")(minute);
-        hnsecs += convert!("seconds", "hnsecs")(second);
-
-        if(negative)
-            hnsecs -= convert!("hours", "hnsecs")(24);
-
-        adjTime = daysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testSTInvalid(SysTime st, int second)
-            {
-                st.second = second;
-            }
-
-            static void testST(SysTime st, int second, in SysTime expected, size_t line = __LINE__)
-            {
-                st.second = second;
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            assertThrown!DateTimeException(testSTInvalid(SysTime(Date(1999, 7, 6)), 60));
-
-            //Test A.D.
-            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 1)));
-            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 7)));
-            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 7), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 7)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 12)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 1), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 7), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 12), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 0, 12)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 0, 5)));
-
-            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(900_000)));
-
-            //Test B.C.
-            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 1)));
-            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 7)));
-            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 12)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 7), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 12), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 7)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 12)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 1), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 7), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 12), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 0, 7)));
-            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 0, 1)));
-
-            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(70)));
-            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(700)));
-            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(7000)));
-            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(70_000)));
-            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(700_000)));
-
-            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 22, 6), FracSec.from!"hnsecs"(9)));
-            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 1), FracSec.from!"hnsecs"(90)));
-            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 1), FracSec.from!"hnsecs"(900)));
-            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 22, 5), FracSec.from!"hnsecs"(9000)));
-            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 1), FracSec.from!"hnsecs"(90_000)));
-            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 22, 23), FracSec.from!"hnsecs"(900_000)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 0, 12), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.seconds = 27));
-            //static assert(!__traits(compiles, ist.seconds = 27));
-        }
-    }
-
-
-    /++
-        Fractional seconds passed the second.
-     +/
-    @property FracSec fracSec() const nothrow
-    {
-        try
-        {
-            auto hnsecs = removeUnitsFromHNSecs!"days"(adjTime);
-
-            if(hnsecs < 0)
-                hnsecs += convert!("hours", "hnsecs")(24);
-
-            hnsecs = removeUnitsFromHNSecs!"seconds"(hnsecs);
-
-            return FracSec.from!"hnsecs"(cast(int)hnsecs);
-        }
-        catch(Exception e)
-            assert(0, "FracSec.from!\"hnsecs\"() threw.");
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0, UTC()).fracSec.hnsecs, 0);
-            assertPred!"=="(SysTime(1, UTC()).fracSec.hnsecs, 1);
-            assertPred!"=="(SysTime(-1, UTC()).fracSec.hnsecs, 9_999_999);
-
-            assertPred!"=="(SysTime(DateTime(200, 3, 30, 1, 27, 19), FracSec.from!"hnsecs"(348), UTC()).fracSec.hnsecs, 348);
-            assertPred!"=="(SysTime(DateTime(-1, 2, 17, 4, 5, 22), FracSec.from!"hnsecs"(347), UTC()).fracSec.hnsecs, 347);
-
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502)).fracSec, FracSec.from!"hnsecs"(502));
-            assertPred!"=="(SysTime(DateTime(0, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502)).fracSec, FracSec.from!"hnsecs"(502));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.fracSec));
-            //static assert(__traits(compiles, ist.fracSec));
-        }
-    }
-
-
-    /++
-        Fractional seconds passed the second.
-
-        Params
-            fracSec = The fractional seconds to set this SysTimes's fractional
-                      seconds to.
-     +/
-    @property void fracSec(FracSec fracSec) nothrow
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs);
-        immutable daysHNSecs = convert!("days", "hnsecs")(days);
-        immutable negative = hnsecs < 0;
-
-        if(negative)
-            hnsecs += convert!("hours", "hnsecs")(24);
-
-        immutable hour = splitUnitsFromHNSecs!"hours"(hnsecs);
-        immutable minute = splitUnitsFromHNSecs!"minutes"(hnsecs);
-        immutable second = getUnitsFromHNSecs!"seconds"(hnsecs);
-
-        hnsecs = fracSec.hnsecs;
-        hnsecs += convert!("hours", "hnsecs")(hour);
-        hnsecs += convert!("minutes", "hnsecs")(minute);
-        hnsecs += convert!("seconds", "hnsecs")(second);
-
-        if(negative)
-            hnsecs -= convert!("hours", "hnsecs")(24);
-
-        adjTime = daysHNSecs + hnsecs;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            static void testST(SysTime st, int hnsecs, in SysTime expected, size_t line = __LINE__)
-            {
-                st.fracSec = FracSec.from!"hnsecs"(hnsecs);
-                assertPred!"=="(st, expected, "", __FILE__, line);
-            }
-
-            //Test A.D.
-            testST(SysTime(Date(1, 1, 1)), 0, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(Date(1, 1, 1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(Date(1, 1, 1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(Date(1, 1, 1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
-
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 0, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(1, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
-
-            testST(SysTime(Date(1, 7, 2)), 12, SysTime(DateTime(1, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(12)));
-            testST(SysTime(Date(5007, 7, 2)), 5, SysTime(DateTime(5007, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(5)));
-
-            testST(SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
-            testST(SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
-
-            testST(SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(999, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(999, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(999, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(999, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
-            testST(SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(999, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(999, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
-
-            //Test B.C.
-            testST(SysTime(Date(0, 1, 1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(Date(0, 1, 1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(Date(0, 1, 1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(Date(0, 1, 1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 0, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12)));
-
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 0, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(0)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 1, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 7, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(1)), 12, SysTime(DateTime(0, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(12)));
-
-            testST(SysTime(Date(0, 7, 2)), 7, SysTime(DateTime(0, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(7)));
-            testST(SysTime(Date(-1202, 7, 2)), 1, SysTime(DateTime(-1202, 7, 2, 0, 0, 0), FracSec.from!"hnsecs"(1)));
-
-            testST(SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(7)), 6, SysTime(DateTime(0, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(70)), 1, SysTime(DateTime(0, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(700)), 1, SysTime(DateTime(0, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(7000)), 5, SysTime(DateTime(0, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
-            testST(SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(70_000)), 1, SysTime(DateTime(0, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(700_000)), 23, SysTime(DateTime(0, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
-
-            testST(SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(9)), 6, SysTime(DateTime(-1, 1, 7, 12, 22, 17), FracSec.from!"hnsecs"(6)));
-            testST(SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(90)), 1, SysTime(DateTime(-1, 1, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(900)), 1, SysTime(DateTime(-1, 2, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(9000)), 5, SysTime(DateTime(-1, 2, 27, 12, 22, 17), FracSec.from!"hnsecs"(5)));
-            testST(SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(90_000)), 1, SysTime(DateTime(-1, 12, 1, 12, 22, 17), FracSec.from!"hnsecs"(1)));
-            testST(SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(900_000)), 23, SysTime(DateTime(-1, 12, 31, 12, 22, 17), FracSec.from!"hnsecs"(23)));
-
-            testST(SysTime(0, UTC()), 12, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(12), UTC()));
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.fracSec = FracSec.from!"msecs"(7)));
-            //static assert(!__traits(compiles, ist.fracSec = FracSec.from!"msecs"(7)));
-        }
-    }
-
-
-    /++
-        The total hnsecs from midnight, January 1st, 1 A.D. UTC. This is the internal
-        representation of SysTime.
-     +/
-    @property long stdTime() const pure nothrow
-    {
-        return _stdTime;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(0).stdTime, 0);
-            assertPred!"=="(SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502), UTC()).stdTime, 330000502L);
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), UTC()).stdTime, 621355968000000000L);
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, cst.stdTime));
-            //static assert(__traits(compiles, ist.stdTime));
-        }
-    }
-
-
-    /++
-        The total hnsecs from midnight, January 1st, 1 A.D. UTC. This is the internal
-        representation of SysTime.
-
-        Params
-            stdTime = The number of hnsecs since January 1st, 1 A.D. UTC.
-     +/
-    @property void stdTime(long stdTime) pure nothrow
-    {
-        _stdTime = stdTime;
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            {
-                auto st = SysTime(0, UTC());
-                st.stdTime = 330000502L;
-                assertPred!"=="(st, SysTime(DateTime(1, 1, 1, 0, 0, 33), FracSec.from!"hnsecs"(502), UTC()));
-            }
-
-            {
-                auto st = SysTime(0, UTC());
-                st.stdTime = 621355968000000000L;
-                assertPred!"=="(st, SysTime(DateTime(1970, 1, 1, 0, 0, 0), UTC()));
-            }
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.stdTime = 27));
-            //static assert(!__traits(compiles, ist.stdTime = 27));
-        }
-    }
-
-
-    /++
-        The current time zone of this SysTime. Its internal time is always kept
-        in UTC, so there are no conversion issues between time zones due to DST.
-        Functions which return all or part of the time - such as hours - adjust
-        the time to this SysTime's time zone before returning.
-      +/
-    @property immutable(TimeZone) timezone() const pure nothrow
-    {
-        return _timezone.get;
-    }
-
-
-    /++
-        The current time zone of this SysTime. It's internal time is always kept
-        in UTC, so there are no conversion issues between time zones due to DST.
-        Functions which return all or part of the time - such as hours - adjust
-        the time to this SysTime's time zone before returning.
-      +/
-    @property void timezone(immutable TimeZone timezone) pure nothrow
-    {
-        _timezone = timezone;
-    }
-
-
-    /++
-        Returns whether DST is in effect for this SysTime.
-      +/
-    @property bool dstInEffect() const nothrow
-    {
-        return _timezone.dstInEffect(_stdTime);
-        //This function's unit testing is done in the time zone classes.
-    }
-
-
-    /++
-        Returns a SysTime with the same std time as this one, but with LocalTime
-        as its time zone.
-      +/
-    SysTime toLocalTime() const nothrow
-    {
-        return SysTime(_stdTime, LocalTime());
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            {
-                auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
-                assertPred!"=="(sysTime, sysTime.toLocalTime());
-                assertPred!"=="(sysTime._stdTime, sysTime.toLocalTime()._stdTime);
-                assert(sysTime.toLocalTime().timezone is LocalTime());
-                assert(sysTime.toLocalTime().timezone is sysTime.timezone);
-                assert(sysTime.toLocalTime().timezone !is UTC());
-            }
-
-            {
-                immutable stz = new SimpleTimeZone(-3 * 60);
-                auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27), stz);
-                assertPred!"=="(sysTime, sysTime.toLocalTime());
-                assertPred!"=="(sysTime._stdTime, sysTime.toLocalTime()._stdTime);
-                assert(sysTime.toLocalTime().timezone is LocalTime());
-                assert(sysTime.toLocalTime().timezone !is UTC());
-                assert(sysTime.toLocalTime().timezone !is stz);
-            }
-        }
-    }
-
-
-    /++
-        Returns a SysTime with the same std time as this one, but with UTC as
-        its time zone.
-      +/
-    SysTime toUTC() const pure nothrow
-    {
-        return SysTime(_stdTime, UTC());
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
-            assertPred!"=="(sysTime, sysTime.toUTC());
-            assertPred!"=="(sysTime._stdTime, sysTime.toUTC()._stdTime);
-            assert(sysTime.toUTC().timezone is UTC());
-            assert(sysTime.toUTC().timezone !is LocalTime());
-            assert(sysTime.toUTC().timezone !is sysTime.timezone);
-        }
-    }
-
-
-    /++
-        Returns a SysTime with the same std time as this one, but with given
-        time zone as its time zone.
-      +/
-    SysTime toOtherTZ(immutable TimeZone tz) const pure nothrow
-    {
-        return SysTime(_stdTime, tz);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            immutable stz = new SimpleTimeZone(11 * 60);
-            auto sysTime = SysTime(DateTime(1982, 1, 4, 8, 59, 7), FracSec.from!"hnsecs"(27));
-            assertPred!"=="(sysTime, sysTime.toOtherTZ(stz));
-            assertPred!"=="(sysTime._stdTime, sysTime.toOtherTZ(stz)._stdTime);
-            assert(sysTime.toOtherTZ(stz).timezone is stz);
-            assert(sysTime.toOtherTZ(stz).timezone !is LocalTime());
-            assert(sysTime.toOtherTZ(stz).timezone !is UTC());
-        }
-    }
-
-
-    /++
-        Returns a time_t which represents this SysTime.
-
-        If time_t is 32 bits, rather than 64, and the result can't fit in a 32-bit
-        value, then the closest value that can be held in 32 bits will be used
-        (so time_t.max if it goes over or time_t.min if it goes under).
-      +/
-    time_t toUnixTime() const pure nothrow
-    {
-        return stdTimeToUnixTime(_stdTime);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(1), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"usecs"(1), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 0), FracSec.from!"msecs"(1), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1970, 1, 1, 0, 0, 1), UTC()).toUnixTime, 1);
-            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999_999), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC()).toUnixTime, 0);
-            assertPred!"=="(SysTime(DateTime(1969, 12, 31, 23, 59, 59), UTC()).toUnixTime, -1);
-        }
-    }
-
-
-    /++
-        Returns a timeval which represents this SysTime.
-
-        If time_t is 32 bits, rather than 64, and the result can't fit in a 32-bit
-        value, then the closest value that can be held in 32 bits will be used
-        for tv_sec. (so time_t.max if it goes over or time_t.min if it goes under).
-      +/
-    timeval toTimeVal() const pure nothrow
-    {
-        immutable tv_sec = toUnixTime();
-
-        immutable fracHNSecs = removeUnitsFromHNSecs!"seconds"(_stdTime - 621355968000000000L);
-        immutable tv_usec = cast(int)convert!("hnsecs", "usecs")(fracHNSecs);
-
-        return timeval(tv_sec, tv_usec);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            assert(SysTime(DateTime(1970, 1, 1), UTC()).toTimeVal() == timeval(0, 0));
-            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"hnsecs"(9), UTC()).toTimeVal() == timeval(0, 0));
-            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"hnsecs"(10), UTC()).toTimeVal() == timeval(0, 1));
-            assert(SysTime(DateTime(1970, 1, 1), FracSec.from!"usecs"(7), UTC()).toTimeVal() == timeval(0, 7));
-
-            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), UTC()).toTimeVal() == timeval(1, 0));
-            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(9), UTC()).toTimeVal() == timeval(1, 0));
-            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"hnsecs"(10), UTC()).toTimeVal() == timeval(1, 1));
-            assert(SysTime(DateTime(1970, 1, 1, 0, 0, 1), FracSec.from!"usecs"(7), UTC()).toTimeVal() == timeval(1, 7));
-
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999), UTC()).toTimeVal() ==
-                   timeval(0, 0));
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"hnsecs"(9_999_990), UTC()).toTimeVal() ==
-                   timeval(0, -1));
-
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999_999), UTC()).toTimeVal() ==
-                   timeval(0, -1));
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"usecs"(999), UTC()).toTimeVal() ==
-                   timeval(0, -999_001));
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), FracSec.from!"msecs"(999), UTC()).toTimeVal() ==
-                   timeval(0, -1000));
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 59), UTC()).toTimeVal() == timeval(-1, 0));
-            assert(SysTime(DateTime(1969, 12, 31, 23, 59, 58), FracSec.from!"usecs"(17), UTC()).toTimeVal() ==
-                   timeval(-1, -999_983));
-        }
-    }
-
-
-    /++
-        Returns a tm which represents this SysTime.
-      +/
-    tm toTM() const nothrow
-    {
-        try
-        {
-            auto dateTime = cast(DateTime)this;
-            tm timeInfo;
-
-            timeInfo.tm_sec = dateTime.second;
-            timeInfo.tm_min = dateTime.minute;
-            timeInfo.tm_hour = dateTime.hour;
-            timeInfo.tm_mday = dateTime.day;
-            timeInfo.tm_mon = dateTime.month - 1;
-            timeInfo.tm_year = dateTime.year - 1900;
-            timeInfo.tm_wday = dateTime.dayOfWeek;
-            timeInfo.tm_yday = dateTime.dayOfYear - 1;
-            timeInfo.tm_isdst = _timezone.dstInEffect(_stdTime);
-
-            version(Posix)
-            {
-                char[] zone = (timeInfo.tm_isdst ? _timezone.dstName : _timezone.stdName).dup;
-                zone ~= "\0";
-
-                timeInfo.tm_gmtoff = cast(int)convert!("hnsecs", "seconds")(adjTime - _stdTime);
-                timeInfo.tm_zone = zone.ptr;
-            }
-
-            return timeInfo;
-        }
-        catch(Exception e)
-            assert(0, "Either DateTime's constructor threw.");
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            version(Posix)
-            {
-                scope(exit) clearTZEnvVar();
-                setTZEnvVar("America/Los_Angeles");
-            }
-
-            {
-                auto timeInfo = SysTime(DateTime(1970, 1, 1)).toTM();
-
-                assertPred!"=="(timeInfo.tm_sec, 0);
-                assertPred!"=="(timeInfo.tm_min, 0);
-                assertPred!"=="(timeInfo.tm_hour, 0);
-                assertPred!"=="(timeInfo.tm_mday, 1);
-                assertPred!"=="(timeInfo.tm_mon, 0);
-                assertPred!"=="(timeInfo.tm_year, 70);
-                assertPred!"=="(timeInfo.tm_wday, 4);
-                assertPred!"=="(timeInfo.tm_yday, 0);
-
-                version(Posix)
-                    assertPred!"=="(timeInfo.tm_isdst, 0);
-                else version(Windows)
-                    assert(timeInfo.tm_isdst == 0 || timeInfo.tm_isdst == 1);
-
-                version(Posix)
-                {
-                    assertPred!"=="(timeInfo.tm_gmtoff, -8 * 60 * 60);
-                    assertPred!"=="(to!string(timeInfo.tm_zone), "PST");
-                }
-            }
-
-            {
-                auto timeInfo = SysTime(DateTime(2010, 7, 4, 12, 15, 7), FracSec.from!"hnsecs"(15)).toTM();
-
-                assertPred!"=="(timeInfo.tm_sec, 7);
-                assertPred!"=="(timeInfo.tm_min, 15);
-                assertPred!"=="(timeInfo.tm_hour, 12);
-                assertPred!"=="(timeInfo.tm_mday, 4);
-                assertPred!"=="(timeInfo.tm_mon, 6);
-                assertPred!"=="(timeInfo.tm_year, 110);
-                assertPred!"=="(timeInfo.tm_wday, 0);
-                assertPred!"=="(timeInfo.tm_yday, 184);
-
-                version(Posix)
-                    assertPred!"=="(timeInfo.tm_isdst, 1);
-                else version(Windows)
-                    assert(timeInfo.tm_isdst == 0 || timeInfo.tm_isdst == 1);
-
-                version(Posix)
-                {
-                    assertPred!"=="(timeInfo.tm_gmtoff, -7 * 60 * 60);
-                    assertPred!"=="(to!string(timeInfo.tm_zone), "PDT");
-                }
-            }
-        }
-    }
-
-
-    /++
-        Adds the given number of years or months to this SysTime. A negative
-        number will subtract.
-
-        Note that if day overflow is allowed, and the date with the adjusted
-        year/month overflows the number of days in the new month, then the month
-        will be incremented by one, and the days set to the number of days overflowed.
-        (e.g. if the day were 31 and the new month were June, then the month would
-        be incremented to July, and the new day would be 1). If day overflow is not
-        allowed, then the day will be set to the last valid day in the month
-        (e.g. June 31st would become June 30th).
-
-        Params:
-            units         = The type of units to add ("years" or "months").
-            value         = The number of months or years to add to this SysTime.
-            allowOverflow = Whether the days should be allowed to overflow, causing
-                            the month to increment.
-
-        Examples:
---------------------
-auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
-st1.add!"months"(11);
-assert(st1 == SysTime(DateTime(2010, 12, 1, 12, 30, 33)));
-
-auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
-st2.add!"months"(-11);
-assert(st2 == SysTime(DateTime(2009, 2, 1, 12, 30, 33)));
-
-auto st3 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
-st3.add!"years"(1);
-assert(st3 == SysTime(DateTime(2001, 3, 1, 12, 30, 33)));
-
-auto st4 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
-st4.add!"years"(1, AllowDayOverflow.no);
-assert(st4 == SysTime(DateTime(2001, 2, 28, 12, 30, 33)));
---------------------
-      +/
-    ref SysTime add(string units)(long years, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
-        if(units == "years" ||
-           units == "months")
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.add!units(years, allowOverflow);
-        days = date.dayOfGregorianCal - 1;
-
-        if(days < 0)
-        {
-            hnsecs -= convert!("hours", "hnsecs")(24);
-            ++days;
-        }
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
-
-        adjTime = newDaysHNSecs + hnsecs;
-
-        return this;
-    }
-
-    //Test add!"years"() with AllowDayOverlow.yes
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"years"(7);
-                assertPred!"=="(sysTime, SysTime(Date(2006, 7, 6)));
-                sysTime.add!"years"(-9);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
-                sysTime.add!"years"(7);
-                assertPred!"=="(sysTime, SysTime(DateTime(2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-                sysTime.add!"years"(-9);
-                assertPred!"=="(sysTime, SysTime(DateTime(1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(2000, 2, 29, 0, 7, 2), FracSec.from!"usecs"(1207));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 3, 1, 0, 7, 2), FracSec.from!"usecs"(1207)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"years"(-7);
-                assertPred!"=="(sysTime, SysTime(Date(-2006, 7, 6)));
-                sysTime.add!"years"(9);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
-                sysTime.add!"years"(-7);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-                sysTime.add!"years"(9);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2000, 2, 29, 3, 3, 3), FracSec.from!"hnsecs"(3));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 3, 1, 3, 3, 3), FracSec.from!"hnsecs"(3)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(4, 7, 6));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 7, 6)));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 7, 6));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(Date(1, 7, 6)));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 7, 6));
-                sysTime.add!"years"(-8);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-                sysTime.add!"years"(8);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 7, 6));
-                sysTime.add!"years"(8);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-                sysTime.add!"years"(-8);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 2, 29));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(Date(1, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 2, 29));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"years"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"years"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 3, 1, 5, 5, 5), FracSec.from!"msecs"(555)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1, 3, 1, 5, 5, 5), FracSec.from!"msecs"(555)));
-            }
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.add!"years"(4)));
-            //static assert(!__traits(compiles, ist.add!"years"(4)));
-
-            //Verify Examples.
-            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
-            st1.add!"months"(11);
-            assert(st1 == SysTime(DateTime(2010, 12, 1, 12, 30, 33)));
-
-            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30, 33));
-            st2.add!"months"(-11);
-            assert(st2 == SysTime(DateTime(2009, 2, 1, 12, 30, 33)));
-
-            auto st3 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
-            st3.add!"years"(1);
-            assert(st3 == SysTime(DateTime(2001, 3, 1, 12, 30, 33)));
-
-            auto st4 = SysTime(DateTime(2000, 2, 29, 12, 30, 33));
-            st4.add!"years"(1, AllowDayOverflow.no);
-            assert(st4 == SysTime(DateTime(2001, 2, 28, 12, 30, 33)));
-        }
-    }
-
-    //Test add!"years"() with AllowDayOverlow.no
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"years"(7, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2006, 7, 6)));
-                sysTime.add!"years"(-9, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
-                sysTime.add!"years"(7, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-                sysTime.add!"years"(-9, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(2000, 2, 29, 0, 7, 2), FracSec.from!"usecs"(1207));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 28, 0, 7, 2), FracSec.from!"usecs"(1207)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"years"(-7, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2006, 7, 6)));
-                sysTime.add!"years"(9, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234));
-                sysTime.add!"years"(-7, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2006, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-                sysTime.add!"years"(9, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1997, 7, 6, 12, 7, 3), FracSec.from!"msecs"(234)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2000, 2, 29, 3, 3, 3), FracSec.from!"hnsecs"(3));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 28, 3, 3, 3), FracSec.from!"hnsecs"(3)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(4, 7, 6));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 7, 6)));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 7, 6));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1, 7, 6)));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 7, 6));
-                sysTime.add!"years"(-8, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-                sysTime.add!"years"(8, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 7, 6));
-                sysTime.add!"years"(8, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 7, 6)));
-                sysTime.add!"years"(-8, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 2, 29));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 2, 29));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"years"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"years"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
-                sysTime.add!"years"(-5);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-                sysTime.add!"years"(5);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-4, 7, 6, 14, 7, 1), FracSec.from!"usecs"(54329)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
-                sysTime.add!"years"(5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 2, 28, 5, 5, 5), FracSec.from!"msecs"(555)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 2, 29, 5, 5, 5), FracSec.from!"msecs"(555));
-                sysTime.add!"years"(-5, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1, 2, 28, 5, 5, 5), FracSec.from!"msecs"(555)));
-            }
-        }
-    }
-
-    //Test add!"months"() with AllowDayOverlow.yes
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(3);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.add!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(6);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 6)));
-                sysTime.add!"months"(-6);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(27);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 10, 6)));
-                sysTime.add!"months"(-28);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 5, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.add!"months"(12);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.add!"months"(12);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 31));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 8, 31));
-                sysTime.add!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
-                sysTime.add!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.add!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 31)));
-                sysTime.add!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 3)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 3, 2)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 3, 3)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.add!"months"(3);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.add!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(2000, 3, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 1, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(2001, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(2000, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(3);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
-                sysTime.add!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(6);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 1, 6)));
-                sysTime.add!"months"(-6);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(-27);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 4, 6)));
-                sysTime.add!"months"(28);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 5, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.add!"months"(-12);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.add!"months"(-12);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 3, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 31));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1998, 8, 31));
-                sysTime.add!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 10, 1)));
-                sysTime.add!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.add!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(-1995, 1, 31)));
-                sysTime.add!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-1995, 3, 3)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-1996, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2002, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 3, 2)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 1, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2001, 12, 31));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 3, 3)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.add!"months"(3);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.add!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 3, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 1, 2, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(1, 1, 1));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(0, 12, 1)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 1, 1));
-                sysTime.add!"months"(-48);
-                assertPred!"=="(sysTime, SysTime(Date(0, 1, 1)));
-                sysTime.add!"months"(48);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.add!"months"(-49);
-                assertPred!"=="(sysTime, SysTime(Date(0, 3, 2)));
-                sysTime.add!"months"(49);
-                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.add!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(Date(-3, 3, 3)));
-                sysTime.add!"months"(85);
-                assertPred!"=="(sysTime, SysTime(Date(4, 4, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
-                sysTime.add!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-                sysTime.add!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.add!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 3, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.add!"months"(85);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 3, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.add!"months"(85);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 5, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.add!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.add!"months"(4)));
-            //static assert(!__traits(compiles, ist.add!"months"(4)));
-
-            //Verify Examples.
-            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 30 ,33));
-            st1.add!"months"(1);
-            assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 30 ,33)));
-
-            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 30 ,33));
-            st2.add!"months"(-1);
-            assert(st2 == SysTime(DateTime(2009, 12, 1, 12, 30 ,33)));
-
-            auto st3 = SysTime(DateTime(1999, 1, 29, 12, 30 ,33));
-            st3.add!"months"(1);
-            assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 30 ,33)));
-
-            auto st4 = SysTime(DateTime(1999, 1, 29, 12, 30 ,33));
-            st4.add!"months"(1, AllowDayOverflow.no);
-            assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 30 ,33)));
-        }
-    }
-
-    //Test add!"months"() with AllowDayOverlow.no
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.add!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 1, 6)));
-                sysTime.add!"months"(-6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.add!"months"(27, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 10, 6)));
-                sysTime.add!"months"(-28, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 4, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.add!"months"(12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.add!"months"(12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 31));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 8, 31));
-                sysTime.add!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
-                sysTime.add!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 8, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.add!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 31)));
-                sysTime.add!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 12, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2001, 2, 28)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.add!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.add!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(2000, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1998, 12, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(2001, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
-                sysTime.add!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 1, 6)));
-                sysTime.add!"months"(-6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.add!"months"(-27, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 4, 6)));
-                sysTime.add!"months"(28, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.add!"months"(-12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.add!"months"(-12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 31));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 9, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1998, 8, 31));
-                sysTime.add!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 9, 30)));
-                sysTime.add!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 8, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.add!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1995, 1, 31)));
-                sysTime.add!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1995, 2, 28)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2002, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2002, 12, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2001, 12, 31));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.add!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.add!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2000, 2, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 12, 29, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.add!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.add!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(1, 1, 1));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(0, 12, 1)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 1, 1));
-                sysTime.add!"months"(-48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(0, 1, 1)));
-                sysTime.add!"months"(48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.add!"months"(-49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(0, 2, 29)));
-                sysTime.add!"months"(49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.add!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-3, 2, 28)));
-                sysTime.add!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
-                sysTime.add!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-                sysTime.add!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.add!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 2, 28, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.add!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 28, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.add!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.add!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-        }
-    }
-
-
-    /++
-        Adds the given number of years to this SysTime. A negative number will
-        subtract.
-
-        For years, because they are the largest unit in SysTime, there is no
-        difference between adding or rolling.
-
-        Params:
-            years         = The number of years to add to this SysTime.
-            allowOverflow = Whether the days should be allowed to overflow,
-                            causing the month to increment.
-      +/
-    /+ref SysTime+/ void roll(string units)(long years, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
-        if(units == "years")
-    {
-        add!"years"(years, allowOverflow);
-    }
-
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            auto st = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(__traits(compiles, st.roll!"years"(4)));
-            static assert(!__traits(compiles, cst.roll!"years"(4)));
-            //static assert(!__traits(compiles, ist.roll!"years"(4)));
-        }
-    }
-
-
-    /++
-        Adds the given number of months to this SysTime. A negative number will
-        subtract.
-
-        The difference between rolling and adding is that rolling does not affect
-        larger units. So, if you roll the SysTime 12 months, you get the exact
-        same SysTime. However, the days can still be affected due to the differing
-        number of days in each month.
-
-        Params:
-            months        = The number of months to add to this SysTime.
-            allowOverflow = Whether the days should be allowed to overflow,
-                            causing the month to increment.
-
-        Examples:
---------------------
-auto st1 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
-st1.roll!"months"(1);
-assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 33, 33)));
-
-auto st2 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
-st2.roll!"months"(-1);
-assert(st2 == SysTime(DateTime(2010, 12, 1, 12, 33, 33)));
-
-auto st3 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
-st3.roll!"months"(1);
-assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 33, 33)));
-
-auto st4 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
-st4.roll!"months"(1, AllowDayOverflow.no);
-assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 33, 33)));
---------------------
-      +/
-    /+ref SysTime+/ void roll(string units)(long months, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) nothrow
-        if(units == "months")
-    {
-        auto hnsecs = adjTime;
-        auto days = splitUnitsFromHNSecs!"days"(hnsecs) + 1;
-
-        if(hnsecs < 0)
-        {
-            hnsecs += convert!("hours", "hnsecs")(24);
-            --days;
-        }
-
-        auto date = Date(cast(int)days);
-        date.roll!"months"(months, allowOverflow);
-        days = date.dayOfGregorianCal - 1;
-
-        if(days < 0)
-        {
-            hnsecs -= convert!("hours", "hnsecs")(24);
-            ++days;
-        }
-
-        immutable newDaysHNSecs = convert!("days", "hnsecs")(days);
-
-        adjTime = newDaysHNSecs + hnsecs;
-    }
-
-    //Test roll!"months"() with AllowDayOverlow.yes
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(3);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.roll!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(6);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 6)));
-                sysTime.roll!"months"(-6);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(27);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.roll!"months"(-28);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 5, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.roll!"months"(12);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.roll!"months"(12);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 31));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 8, 31));
-                sysTime.roll!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 10, 1)));
-                sysTime.roll!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.roll!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 31)));
-                sysTime.roll!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.roll!"months"(3);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.roll!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(1998, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(1998, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(3);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
-                sysTime.roll!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(6);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 6)));
-                sysTime.roll!"months"(-6);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(-27);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 6)));
-                sysTime.roll!"months"(28);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 5, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.roll!"months"(-12);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.roll!"months"(-12);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 31));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1998, 8, 31));
-                sysTime.roll!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 10, 1)));
-                sysTime.roll!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.roll!"months"(13);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 31)));
-                sysTime.roll!"months"(-13);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2002, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-2002, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-2002, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2001, 12, 31));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 3, 3)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 1, 3)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007));
-                sysTime.roll!"months"(3);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007)));
-                sysTime.roll!"months"(-4);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"hnsecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 3, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 1, 3, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(1, 1, 1));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(1, 12, 1)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 1, 1));
-                sysTime.roll!"months"(-48);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-                sysTime.roll!"months"(48);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.roll!"months"(-49);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 2)));
-                sysTime.roll!"months"(49);
-                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.roll!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 2)));
-                sysTime.roll!"months"(85);
-                assertPred!"=="(sysTime, SysTime(Date(4, 4, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1, 1, 1));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 12, 1)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 1, 1));
-                sysTime.roll!"months"(-48);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
-                sysTime.roll!"months"(48);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 3, 31));
-                sysTime.roll!"months"(-49);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 2)));
-                sysTime.roll!"months"(49);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 4, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 3, 31));
-                sysTime.roll!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 2)));
-                sysTime.roll!"months"(85);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 4, 2)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
-                sysTime.roll!"months"(-1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-                sysTime.roll!"months"(1);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.roll!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 2, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.roll!"months"(85);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 4, 2, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.roll!"months"(85);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 5, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.roll!"months"(-85);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 1, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            const cst = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            //immutable ist = SysTime(DateTime(1999, 7, 6, 12, 30, 33));
-            static assert(!__traits(compiles, cst.roll!"months"(4)));
-            //static assert(!__traits(compiles, ist.roll!"months"(4)));
-
-            //Verify Examples.
-            auto st1 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
-            st1.roll!"months"(1);
-            assert(st1 == SysTime(DateTime(2010, 2, 1, 12, 33, 33)));
-
-            auto st2 = SysTime(DateTime(2010, 1, 1, 12, 33, 33));
-            st2.roll!"months"(-1);
-            assert(st2 == SysTime(DateTime(2010, 12, 1, 12, 33, 33)));
-
-            auto st3 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
-            st3.roll!"months"(1);
-            assert(st3 == SysTime(DateTime(1999, 3, 1, 12, 33, 33)));
-
-            auto st4 = SysTime(DateTime(1999, 1, 29, 12, 33, 33));
-            st4.roll!"months"(1, AllowDayOverflow.no);
-            assert(st4 == SysTime(DateTime(1999, 2, 28, 12, 33, 33)));
-        }
-    }
-
-    //Test roll!"months"() with AllowDayOverlow.no
-    unittest
-    {
-        version(testStdDateTime)
-        {
-            //Test A.D.
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.roll!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 1, 6)));
-                sysTime.roll!"months"(-6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 6));
-                sysTime.roll!"months"(27, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 10, 6)));
-                sysTime.roll!"months"(-28, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 6, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 5, 31));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 4, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 2, 28));
-                sysTime.roll!"months"(12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(2000, 2, 29));
-                sysTime.roll!"months"(12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(2000, 2, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 7, 31));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 8, 31)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 9, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 8, 31));
-                sysTime.roll!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 9, 30)));
-                sysTime.roll!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 8, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.roll!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 1, 31)));
-                sysTime.roll!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1997, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1997, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1998, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1998, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(1999, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1999, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.roll!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.roll!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1998, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1998, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1998, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1999, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1999, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test B.C.
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 10, 6)));
-                sysTime.roll!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 1, 6)));
-                sysTime.roll!"months"(-6, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 7, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 6));
-                sysTime.roll!"months"(-27, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 6)));
-                sysTime.roll!"months"(28, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 6)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 6, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 5, 31));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 4, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 2, 28));
-                sysTime.roll!"months"(-12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 2, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2000, 2, 29));
-                sysTime.roll!"months"(-12, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2000, 2, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1999, 7, 31));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 8, 31)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1999, 9, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1998, 8, 31));
-                sysTime.roll!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 9, 30)));
-                sysTime.roll!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1998, 8, 30)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.roll!"months"(13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 1, 31)));
-                sysTime.roll!"months"(-13, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 31)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1997, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1997, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2002, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2002, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2002, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-2001, 12, 31));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 2, 28)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-2001, 12, 28)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-1999, 7, 6, 12, 2, 7), FracSec.from!"usecs"(5007));
-                sysTime.roll!"months"(3, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 10, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-                sysTime.roll!"months"(-4, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-1999, 6, 6, 12, 2, 7), FracSec.from!"usecs"(5007)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2002, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2002, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-2001, 12, 31, 7, 7, 7), FracSec.from!"hnsecs"(422202));
-                sysTime.roll!"months"(14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 2, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-                sysTime.roll!"months"(-14, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-2001, 12, 28, 7, 7, 7), FracSec.from!"hnsecs"(422202)));
-            }
-
-            //Test Both
-            {
-                auto sysTime = SysTime(Date(1, 1, 1));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1, 12, 1)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 1, 1));
-                sysTime.roll!"months"(-48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-                sysTime.roll!"months"(48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.roll!"months"(-49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 2, 29)));
-                sysTime.roll!"months"(49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(4, 3, 31));
-                sysTime.roll!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 2, 29)));
-                sysTime.roll!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(4, 3, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-1, 1, 1));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 12, 1)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-1, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 1, 1));
-                sysTime.roll!"months"(-48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
-                sysTime.roll!"months"(48, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 1, 1)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 3, 31));
-                sysTime.roll!"months"(-49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 2, 29)));
-                sysTime.roll!"months"(49, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(Date(-4, 3, 31));
-                sysTime.roll!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 2, 29)));
-                sysTime.roll!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(Date(-4, 3, 29)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 0, 0, 0), FracSec.from!"hnsecs"(0)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 1, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(0, 12, 1, 23, 59, 59), FracSec.from!"hnsecs"(9_999_999)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17));
-                sysTime.roll!"months"(-1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 12, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-                sysTime.roll!"months"(1, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(1, 1, 1, 0, 7, 9), FracSec.from!"hnsecs"(17)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(4, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.roll!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 2, 29, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.roll!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(4, 3, 29, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-
-            {
-                auto sysTime = SysTime(DateTime(-3, 3, 31, 12, 11, 10), FracSec.from!"msecs"(9));
-                sysTime.roll!"months"(85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 4, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
-                sysTime.roll!"months"(-85, AllowDayOverflow.no);
-                assertPred!"=="(sysTime, SysTime(DateTime(-3, 3, 30, 12, 11, 10), FracSec.from!"msecs"(9)));
-            }
-        }
-    }
-
-
-    /++
-        Adds the given number of days to this SysTime. A negative number will
-        subtract.
-
-        The difference between rolling and adding is that rolling does not affect
-        larger units. So, if you roll the SysTime one year's worth of days, then
-        you get the exact same SysTime.
-
-        Note that TimeOfDay has no $(D add!"days"()) function because you can add
-        days to a SysTime by adding a duration to it.
-
-        Params:
-            days = The number of days to add to this SysTime.
-
-        Examples:
---------------------
-auto st = SysTime(DateTime(2010, 1, 1, 11, 23, 12));
-st.roll!"days"(1);
-assert(st == SysTime(DateTime(2010, 1, 2, 11, 23, 12)));
-st.roll!"days"(365);
-assert(st == SysTime(DateTime(2010, 1, 26, 11, 23, 12)));
-st.roll!"days"(-32);
-assert(st == SysTime(DateTime(2010, 1, 25, 11, 23, 12)));
---------------------
-      +/
-    /+ref SysTime+/ void roll(string units)(long days) nothrow
-        if(units == "days")
-    {
-        auto hnsecs = adjTime;
-        auto gdays = splitUnitsFromHNSecs!"days"(hnsecs) + 1;