Maybe this is naive, but the younger you are, the larger the ratio of each unit of time to your total time lived. So each unit of time seems longer.
I used to think sitting through a 3 hour lecture was an eternity. Now after sitting at a desk for 10 hours a day 3 hours is just seen as a morning.
When you are 4, turning 5 is another 20-25% of your life. When you're 39, turning 40 is more like .025% of your life.
Perception of time changes because we have more of it to compare it to, making it feel like its accelerating. But that is all relative.
Speaking of getting older, what's with the incredibly tiny fonts on web sites these days? I can read it OK, but Ctrl + makes it less annoying. If they're trying to "fit more ads" it's backfiring in my case because I'm less likely to read it. Now get off my lawn.