Time dilation is a really trippy phenomenon that also occurs when you move really fast, which is the reason why astronauts after travelling in the ISS at 7km/second for 6 months come back down to Earth about 0.007 seconds younger than everyone else. That might sound like nothing, but for GPS satellites to work they have to know the exact time within nanoseconds, and so if they used the same clocks we use on Earth, the GPS would progressively get more and more inaccurate at a rate of 10km a day!