What was the thing that made you think "man I'm getting old"

Mine was a recently event. I hit the new first digit this year so that's one too... But not the one that made me think about it.

I was a band geak in high school. Still kinda am. My high school has an annual alumni pep band night. I was looking at the high schoolers and realized I could easily be any of their parents. And that I was one of the oldest alumni there this year (but not oldest. A few were older). A few of the others who I went to HS and marched with were band parents.