I've been told that the subjective midpoint of your life is age seventeen (yikes!). Time crawls when you're young, but goes faster than a speeding bullet train as you hit your thirties.
New research may cast doubt on this, however:
Age accounted for four per cent of the variance in how quickly participants said the last ten years had passed and just one per cent of the perception of time's speed in general. By contrast, how busy and rushed people reported feeling accounted for ten per cent of the variance in subjective speed of time. Consistent with this, women reported feeling more rushed than men, on average, and they perceived time to go by more quickly.
So it's not youth that slows our time perception, but the fact that grammar and middle school involve incredibly long stretches of boredom. You could probably get the same subjective effect by going to work on the right sort of assembly line. It seems like the only way to get more subjective years is to make each one of them worth less.
But we might get a few worthy extra subjective moments if we stopped to smell the flowers a little more frequently.