Whilst two observers moving relative to each other will experience the other’s time as moving slower or faster (Einstein’s Theory of Special Relativity), the passage of time for any given observer in a single reference frame is constant.

But as you get older, time seems to go faster. This is because each subsequent day is a smaller fraction of your lifetime up to that point: for a one year-old baby, one day represents 0.274% of their lifetime; but for an eighty year-old adult one day is a mere 0.00343%.

The progression is easier to see on a logarithmic scale: