DateTime.utc(int year, [int month = 1, int day = 1, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0])

Constructs a DateTime instance specified in the UTC time zone.

DateTime dDay = new DateTime.utc(1944, DateTime.JUNE, 6);

Source 

DateTime.utc(int year,
             [int month = 1,
              int day = 1,
              int hour = 0,
              int minute = 0,
              int second = 0,
              int millisecond = 0,
              int microsecond = 0])
  : this._internal(
        year, month, day, hour, minute, second, millisecond, microsecond,
        true);