The way time seems to speed by these days I am reminded of a theory I heard many years ago. As you get older time seems to speed up. This appears to happen because each year added to your life becomes less of a percentage of a total life experience. One year is one half of a two year old child's life. By the time they reach 20 one year is reduced to 1/20th of the experience making it appear to go faster.
This has always made sense to me!