public bool TryGetNext(DateTimeOffset value, TimeZoneInfo tz, out DateTimeOffset result)
{
if (tz is null)
{
throw new ArgumentNullException(nameof(tz));
}
result = DateTimeOffset.MinValue;
var current = value.DateTime;
var acceptCurrent = false;
// vixie cron + wikipedia
if (tz.IsAmbiguousTime(value))
{
var periodEnd = tz.GetCurrentPeriodEnd(current);
var periodEndOffset = periodEnd.Offset;
var periodEndValue = periodEnd.DateTime;
var otherOffset = tz.GetOtherAmbigousOffset(periodEnd);
// is DST?
if (otherOffset != value.Offset)
{
if (!TryGetNextInstant(current, acceptCurrent, out var guess))
{
return(false);
}
if (guess < periodEndValue)
{
result = new DateTimeOffset(guess, periodEndOffset);
return(true);
}
// start of the ambigous period
// Magadan Standard Time has +11 as base,
// but they shifted from 12 to 10 at 2014, 10, 26, 0, 0, 0
current = periodEnd.ToOffset(otherOffset).DateTime;
acceptCurrent = true;
}
if (hasInterval)
{
// iterate the transition period
if (!TryGetNextInstant(current, acceptCurrent, out var guess))
{
return(false);
}
if (guess < periodEndValue)
{
result = new DateTimeOffset(guess, otherOffset);
return(true);
}
}
current = periodEndValue;
acceptCurrent = true;
}
while (true)
{
if (!TryGetNextInstant(current, acceptCurrent, out var retval))
{
return(false);
}
if (tz.IsInvalidTime(retval))
{
current = retval;
continue;
}
result = tz.IsAmbiguousTime(retval)
? new DateTimeOffset(retval, tz.GetCurrentPeriodEnd(retval).Offset)
: new DateTimeOffset(retval, tz.GetUtcOffset(retval));
return(true);
}
}