The way we experience time depends on our age which is why the older we get, the faster it goes.

I think it's also a question of new experiences, in that doing something unchallenging and familiar = no time passes, whereas doing something unfamiliar = subjectively time is created to accommodate the new experience.

I didn't express that well, but it is easy to see in personal experience. Spend a day doing the same old same old and it whips through like nothing. Spend the day doing something totally demanding and at the end of the day it feels like a full day has passed for a change.