New research suggests why time seems to speed up or slow down.

In experiments, psychologists found that subjects underestimated how much time had passed by three months, but the more intervening related developments came to mind, the longer away the original event seemed.

They also found that when people were tricked into believing that more time had passed than was really the case, they assumed they must have been having more fun. The perception heightened their enjoyment of music and eased their annoyance at doing menial tasks.