The number of microseconds since the "Unix epoch" 1970-01-01T00:00:00Z (UTC).
This value is independent of the time zone.
This value is at most 8,640,000,000,000,000,000us (100,000,000 days) from the Unix epoch. In other words: microsecondsSinceEpoch.abs() <= 8640000000000000000.
@override int get microsecondsSinceEpoch => _native.microsecondsSinceEpoch;