In this case, this would be time zone shenanigans. These are decided by big governments doing governmenty things, but the universe doesn’t care about what our politicians think. Time ticks at the same rate it always does for everyone. Look at a time zone map if you have the time, it’s very interesting to see chunks being carved out for different political entities!

If you were travelling near the speed of light OR were very close to a strong gravitational field (like a black hole), time runs, to a stationary observer, much slower than on Earth. You don’t feel anything, the clock runs just as fast as it usually does. But if an astronaut coming back after such conditions would see their twin become much older. If you’re interested in this kind of stuff, check out the movie Interstellar! A lot of it revolves around exploring worlds near black holes, so you get really weird physics! Very good movie I think.