subtract method
Returns a copy of this with the duration
subtracted, wrapping around midnight.
OffsetTime(Offset(8), 12).subtract(Duration(hours: -1)); // 13:00+08:00
OffsetTime(Offset(8), 4).subtract(Duration(hours: 6)); // 22:00+08:00
Implementation
@useResult OffsetTime subtract(Duration duration) => OffsetTime._(offset, _native.subtract(duration));