I've realised lately that every year of my life seems to go by faster than the year before. Then it hit me....

Imagine you are a four year old. Relatively speaking, what fraction of your lifetime does one year account for? A whopping one quarter. Now, if you are a 25, a year amounts to an insignificant 4% of your lifetime, and this percentage decreases with age...

The point is that as we get older, we tend to think of our lifetime, that is, the years that have already passed us as a constant period. This can be perhaps because the amount of things we remember is pretty much the same throughout. (ie. memories get archived into the back of your mind)

To make things worse, the more boring and repetitive your life becomes the more "constant" your previous experience seems to be (i.e. nothing changed) and thus the years zoom by even quicker and become more and more insignificant.

Maybe this perception of time also stems from the fact that in the first decade of your life you learn much more than in the following decades. This makes your first years much more "dense" than the rest, also giving you the impression that time went by slower in the beginning.