But then if all your kill switches are killing then GPS itself will be disabled.
So there always needs to be a mode upon boot-up that just asks the user to enter the date and time. 
None of this need apply unless the phone battery has gone flat.
I understand what you are saying. It may be something of a niche requirement though.
(Note that this is a display issue only. The time is internally in UTC and does not jump around just because you crossed a city bridge or roamed to a different tower.)