Glitches?
There was this one time when I glanced at the clock and it showed 10:30 am... or something like that. I even got surprised how time flies by so fast. Then after a few minutes, I looked again, and it was only 10:10 am-ish.

Or another case was with my HDD space where I was doing headmath to estimate how much space I have left on it (the numbers varied from the usual). Again, a few moments later I check the numbers, and they were the usual numbers.