What is "Time's up"?

What is the meaning of "Time's Up"? For me, time's up is that you don't have any more time on one thing, on the other hand it means that it's over. There is a bunch of example for time's up, like, competition, late or not, or when a season end,etc. The most excited of time's up for me is when you are in a competition, the reason I though that is because you will start to be nervous, and afraid that you might fall. But remember, make sure to do your best every time, if unfortunately, you don't have any time you should at least "try".