Constructs a new DateTime instance
with the given millisecondsSinceEpoch.
If isUtc is false then the date is in the local time zone.
The constructed DateTime represents
1970-01-01T00:00:00Z + millisecondsSinceEpoch ms in the given
time zone (local or UTC).
Source
external DateTime.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch,
{bool isUtc: false});