Engineer Adrian Bejan thinks time seems to speed up as we age because of physical deterioration of our eyes and brains. He might be onto something. I think it’s also because a) when you’re a kid, you’re living completely in the now without all the regrets and worries that come with adulting, and b) when you’re ten, a year is a much bigger chunk of your life than when you’re fifty. Whichever way, it’s all perception.