What about saving the present time (the datetime when the information is recorded) and the time offset as calculated at that moment? In theory then it doesn't m

What about saving the present time (the datetime when the information is recorded) and the time offset as calculated at that moment? In theory then it doesn't matter what happens, you're still able to adjust. The only ambiguity I can think of is if leap (seconds|hours|days) are introduced, but surely you just add them on to the delta too? Of course, this system fails when you suddenly travel anything approaching relativistic speeds, but I guess you could save your time delta as a velocity-time delta :) Edit: I'm not actually advocating this as a solution, I just found it an interesting thought experiment.