LocalZone

// System.LocalZone — System.Core (decompiled from Larva HIR)

into namespace System
{
	/// The local time zone's offset from UTC, asked of the system once per quarter hour of UTC (zones change their offset
	/// only on quarter hours).
	static class LocalZone
	{
		i64 quarter = -9223372036854775808;
		i64 cached;

		extern("time.offset") OffsetAt(i64 seconds) : i64;

		public:
			/// The offset in ticks at a UTC moment (ticks since 0001).
			Offset(i64 utcTicks) : i64
			{
				i64 seconds = utcTicks / 10000000 - 62135596800;
				i64 at = seconds >= 0 ? seconds / 900 : (seconds - 899) / 900;
				if (at != quarter)
				{
					cached = OffsetAt(seconds) * 10000000;
					quarter = at;
				}
				return cached;
			}

			/// The offset in ticks at a local moment: the offset at the moment it would be in UTC, checked once more
			/// (near a change the two can differ).
			OffsetOfLocal(i64 localTicks) : i64
			{
				i64 first = Offset(localTicks);
				i64 second = Offset(localTicks - first);
				return second;
			}
	}
}