Related, I was just talking about why middle/high school years seem to last longer than now. The variety of the time spent was probably a factor (Playing in the band one day, focusing on decathlon another). Life is monotonous these days.

Yes, I have a theory that the perception of time is very closely matched with your perception of novelty. New things, extend the perception of time. Seeing new lands, new people, new experiences, all place landmarks in your memory that make time real. When the days just blurr into each other your brain has a very hard time perceiving the time that went by. All of a sudden, a year is gone. You think about that year, and it seems like it just flew by because well, you have no mental landmarks to remember.

This is why time moves so much slower as a kid. Everything is new then.