Why does time seem to fly when we are having fun?

Time feels fast during fun because your brain is busy with the game, story, or conversation instead of monitoring minutes. With less attention on waiting and fewer mental check-ins, the stretch can seem short while it is happening, even though the clock has not sped up.

Later, the same afternoon may feel full because the best parts are easy to picture again. A dull wait can do the opposite: it seems long in the chair, then leaves only a thin memory behind, like a page with hardly any drawings.