system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Does The Flash always need to re-set his watch?

He regularly reaches relativistic speeds, which should make time pass more slowly for him than the rest of the world. If he's wearing a watch, it would appear to be slow (ironically).
gpt
Maintaining temporal relativity seems to be one of the benefits of the Speed Force for speedsters. The most interesting thing is it seems to be an at will thing, or relative to their rate of speed. There have been some instances of speedsters exceeding this and aging to death within seconds, but it's far more rare than one would expect.

Given this, they should only have to keep track of timezones like the rest of us, as long as they don't exceed the Speed Force's protective abilities.