This is a game which can be played with any digital clock. It's pretty simple really. The object is to find as many consecutive minutes as possible where the numbers on the left add up to the last digit on the right.
1:11: 1 * 1 = 1
1:12: 1 + 1 = 2
That's 2 in a row. I think I've probably found at most 6 minutes in a row. Of course the rules aren't really very concrete, so depending on how mathematically advanced it becomes the easier it will be. Personally, I think integers should be allowed (1:21: 1 - 2 = -1), perhaps even powers (2:38: 2^3 = 8), but if you were to add too many special cases it wouldn't be fun anymore.
And yes, I think you are most likely officially a geek if you enjoy this game.