The international date line runs across the middle of Pacific Ocean opposite (12 hour ahead or before Greenwich mean time (zulu)) Zulu time. It is the boundary where 24 hours elapses and the date changes. I am trying to clear the fog in my mind how pilots account for the date on their flight plan when the flights cross Zulu+-12.
When you file a flight plan, you don't enter an arrival date or time. You just enter proposed UTC departure time and estimated length of time enroute. For aircraft or pilot logbooks we only use UTC date and time for departure, and UTC date and time for arrival. The local arrival date or time does not matter. The international date line has no bearing on UTC date or time.