toUtc method
Returns this DateTime value in the UTC time zone.
Returns this DateTime if it is already in UTC. Otherwise this method is equivalent to:
DateTime.fromMicrosecondsSinceEpoch(microsecondsSinceEpoch,
isUtc: true)
Implementation
@override
// ignore: invalid_use_of_protected_member
UtcDateTime toUtc() => _utc ??= UtcDateTime(year, month, day)..datePart = this;