Just do new things. Go to new places, talk to new people, try new things. It can be as simple as not taking the same route to work/grocery store/etc every time. Mix it up.

Some claim that time feels quicker as you get older because each passing minute is a smaller and smaller portion of your life(e.g. summer for a 6 year old is 5% of their life, whereas it is only half a percent of the life of a 50 year old). But I don't buy that.

Time goes quicker as you get older because people get stuck in the same routine, and it is quite easy to compress memories together when you do the same thing every day. So, go explore, every day, even if it is just mental exploration through books or music, and time will surely slow down.