private DateTimeOffset?GetOccurrenceByZonedTimes(DateTimeOffset from, TimeZoneInfo zone, bool inclusive)
{
var fromLocal = from.DateTime;
if (TimeZoneHelper.IsAmbiguousTime(zone, fromLocal))
{
var currentOffset = from.Offset;
var standardOffset = zone.BaseUtcOffset;
if (standardOffset != currentOffset)
{
var daylightOffset = TimeZoneHelper.GetDaylightOffset(zone, fromLocal);
var daylightTimeLocalEnd = TimeZoneHelper.GetDaylightTimeEnd(zone, fromLocal, daylightOffset).DateTime;
// Early period, try to find anything here.
var foundInDaylightOffset = FindOccurrence(fromLocal.Ticks, daylightTimeLocalEnd.Ticks, inclusive);
if (foundInDaylightOffset != NotFound)
{
return(new DateTimeOffset(foundInDaylightOffset, daylightOffset));
}
fromLocal = TimeZoneHelper.GetStandardTimeStart(zone, fromLocal, daylightOffset).DateTime;
inclusive = true;
}
// Skip late ambiguous interval.
var ambiguousIntervalLocalEnd = TimeZoneHelper.GetAmbiguousIntervalEnd(zone, fromLocal).DateTime;
if (HasFlag(CronExpressionFlag.Interval))
{
var foundInStandardOffset = FindOccurrence(fromLocal.Ticks, ambiguousIntervalLocalEnd.Ticks - 1, inclusive);
if (foundInStandardOffset != NotFound)
{
return(new DateTimeOffset(foundInStandardOffset, standardOffset));
}
}
fromLocal = ambiguousIntervalLocalEnd;
inclusive = true;
}
var occurrenceTicks = FindOccurrence(fromLocal.Ticks, inclusive);
if (occurrenceTicks == NotFound)
{
return(null);
}
var occurrence = new DateTime(occurrenceTicks);
if (zone.IsInvalidTime(occurrence))
{
var nextValidTime = TimeZoneHelper.GetDaylightTimeStart(zone, occurrence);
return(nextValidTime);
}
if (TimeZoneHelper.IsAmbiguousTime(zone, occurrence))
{
var daylightOffset = TimeZoneHelper.GetDaylightOffset(zone, occurrence);
return(new DateTimeOffset(occurrence, daylightOffset));
}
return(new DateTimeOffset(occurrence, zone.GetUtcOffset(occurrence)));
}
private DateTimeOffset?GetOccurrenceConsideringTimeZone(DateTimeOffset fromUtc, TimeZoneInfo zone, bool inclusive)
{
if (!DateTimeHelper.IsRound(fromUtc))
{
// Rarely, if fromUtc is very close to DST transition, `TimeZoneInfo.ConvertTime` may not convert it correctly on Windows.
// E.g., In Jordan Time DST started 2017-03-31 00:00 local time. Clocks jump forward from `2017-03-31 00:00 +02:00` to `2017-03-31 01:00 +3:00`.
// But `2017-03-30 23:59:59.9999000 +02:00` will be converted to `2017-03-31 00:59:59.9999000 +03:00` instead of `2017-03-30 23:59:59.9999000 +02:00` on Windows.
// It can lead to skipped occurrences. To avoid such errors we floor fromUtc to seconds:
// `2017-03-30 23:59:59.9999000 +02:00` will be floored to `2017-03-30 23:59:59.0000000 +02:00` and will be converted to `2017-03-30 23:59:59.0000000 +02:00`.
fromUtc = DateTimeHelper.FloorToSeconds(fromUtc);
inclusive = false;
}
var from = TimeZoneInfo.ConvertTime(fromUtc, zone);
var fromLocal = from.DateTime;
if (TimeZoneHelper.IsAmbiguousTime(zone, fromLocal))
{
var currentOffset = from.Offset;
var standardOffset = zone.BaseUtcOffset;
if (standardOffset != currentOffset)
{
var daylightOffset = TimeZoneHelper.GetDaylightOffset(zone, fromLocal);
var daylightTimeLocalEnd = TimeZoneHelper.GetDaylightTimeEnd(zone, fromLocal, daylightOffset).DateTime;
// Early period, try to find anything here.
var foundInDaylightOffset = FindOccurrence(fromLocal.Ticks, daylightTimeLocalEnd.Ticks, inclusive);
if (foundInDaylightOffset != NotFound)
{
return(new DateTimeOffset(foundInDaylightOffset, daylightOffset));
}
fromLocal = TimeZoneHelper.GetStandardTimeStart(zone, fromLocal, daylightOffset).DateTime;
inclusive = true;
}
// Skip late ambiguous interval.
var ambiguousIntervalLocalEnd = TimeZoneHelper.GetAmbiguousIntervalEnd(zone, fromLocal).DateTime;
if (HasFlag(CronExpressionFlag.Interval))
{
var foundInStandardOffset = FindOccurrence(fromLocal.Ticks, ambiguousIntervalLocalEnd.Ticks - 1, inclusive);
if (foundInStandardOffset != NotFound)
{
return(new DateTimeOffset(foundInStandardOffset, standardOffset));
}
}
fromLocal = ambiguousIntervalLocalEnd;
inclusive = true;
}
var occurrenceTicks = FindOccurrence(fromLocal.Ticks, inclusive);
if (occurrenceTicks == NotFound)
{
return(null);
}
var occurrence = new DateTime(occurrenceTicks);
if (zone.IsInvalidTime(occurrence))
{
var nextValidTime = TimeZoneHelper.GetDaylightTimeStart(zone, occurrence);
return(nextValidTime);
}
if (TimeZoneHelper.IsAmbiguousTime(zone, occurrence))
{
var daylightOffset = TimeZoneHelper.GetDaylightOffset(zone, occurrence);
return(new DateTimeOffset(occurrence, daylightOffset));
}
return(new DateTimeOffset(occurrence, zone.GetUtcOffset(occurrence)));
}