I did this Cow Animation a while ago with a good friend of mine. I am amazed at how fast time flies. I read somewhere that the older you get, the cooler you run (in other words, your core temperature cools as you get older). This may slow your reaction time, thus making it appear time is moving faster. My son told me he is convinced he was eight years old for way longer than a year. I feel like I blinked and he was nine.
I had a dream the other night that my oldest was four again and we were watching TV. In the dream, I put my hand between his shoulder blades like I used to and I could feel his tiny little spine on the tips of my fingers.
What a gift that was.