You know they have to use relativistic physics when syncing time with satelities across the Earth. Those satelites are using ceseum beam timers, or something similarish, and yeah relativity comes into it. In fact, syncing time from bases on the moon with earth is kind of a pain, there was some recent stuff on that as that is where we head next.
If ya look at the math, it’s pretty friggin advanced stuff. Lot’s of this with that and all this other stuff to come up with a ‘simple’ way of basic time syncing. Crazy stuff, real life. Basic agreed upon time is kinda what allows all this nutty internet/cell phone/space stuff to work together across vast distances.