Three things about our perception and experience of time:

1) Current time seems to move faster or slower depending upon the intensity of our experience. If you've ever spent an entire day fishing and didn't get a bite, it seemed like the longest day in history. On the other hand, the day when they were biting like crazy seemed to fly by.

2) Past time is experienced in exactly the reverse fashion of current time. When we reflect back upon those two days of fishing, the day we got skunked has mercifully shrunk down to a barely remembered instance while the day we caught the limit has grown in our memories, just like the size of the fish we caught.

3) Our experience of any span of time is not relative to our previous experience of a similar time-span, but to our cumulative experience. At age ten, a year is 1/10 of one's lifetime, which is a pretty big chunk. At age fifty, a year is only 1/50 one's lifetime, which is inconsequential. So, if each year seems like it's shorter than the last one it's because, relative to our lifetimes, it is!