Why Does Time Seem to Fly as We Get Older? - The Crux
http://blogs.discovermagazine.com/crux/2016/08/11/why-time-flies-older-you-get/
There are several theories which attempt to explain why our perception of time speeds up as we get older. One idea is a gradual alteration of our internal
biological clocks. The slowing of our metabolism as we get older matches the slowing of our heartbeat and our breathing. Children’s biological pacemakers beat
more quickly, meaning that they experience more biological markers (heartbeats, breaths) in a fixed period of time, making it feel like more time has passed.
Another theory suggests that the passage of time we perceive is related to the amount of new perceptual information we absorb. With lots of new stimuli our
brains take longer to process the information so that the period of time feels longer. This would help to explain the “slow motion perception” often reported
in the moments before an accident. The unfamiliar circumstances mean there is so much new information to take in.