Creates a new #GDateTime corresponding to the same instant in time as datetime, but in UTC.
This call is equivalent to calling glib.date_time.DateTime.toTimezone with the time zone returned by glib.time_zone.TimeZone.newUtc.
the newly created #GDateTime which should be freed with glib.date_time.DateTime.unref, or null
Creates a new #GDateTime corresponding to the same instant in time as datetime, but in UTC.
This call is equivalent to calling glib.date_time.DateTime.toTimezone with the time zone returned by glib.time_zone.TimeZone.newUtc.