What really makes me feel old is realising Jurassic Park is as ancient to my son now as the early 1960's movies my parents would show me from their childhood when I was a kid.
The other day I made a reference to something from Jurassic Park at work to a fresh graduate, and got a blank stare. So I say "You know, from Jurassic Park". And was told "Oh, I've never seen it".
I have never felt older than in that moment.
How's this: if you're over 27 years old, you were born closer to the moon landing than the present day.