The other day I had to explain to someone what a ‘Hippie’ was.
I had referred to someone as a ‘leftover hippie’ and got a blank stare in response, followed by being asked what a hippie was.
Yu know you’re getting old when the Sweet Young Things at the gym hold the door open for you. And you’re grateful.
When mention of Pete Seeger and Joan Baez gets you a blank stare. Actually, you know you are getting old when you pass your 79th birthday as I did last week.
You know you’re getting old when you drop something on the floor and decide you don’t need it any time soon.
When you look back at the silly and/or ignorant things your parents said that you were pretty sure were questionable even when you were young. Then you realize that yes, they really didn’t know what they were talking about, but that’s okay, because you are much older and thus understandably wiser than they were when they said those things and were supposedly the wise adult.
You know you’re getting old when you have to explain why 9/11 and 911 are separate things!
You see a group of 20 something’s and instead of thinking they’re hot you want to tell them to put on some clothes.
**You Know You’re Getting Old When… **
You were a hippie.
You Know You’re Getting Old When: Your doctor starts taking you seriously…
You walk into a crowded coffee shop and realize you’re the oldest person in there. Then you hear one girl say to another “Tell her to text me sometime and we’ll all get drunk together” and you think “WTF - you’re like 15 - go home and play with Barbies!!”
**You Know You’re Getting Old When. . . **
. . . Your youngest kid starts complaining about getting old. Not that he isn’t a little premature on that. He hasn’t hit forty yet.
Which reminds me, when my middle boy was in his twenties, he asked me when I stopped listening to new music. It annoyed me greatly, but he was being serious. I got to remind him of it a few years ago and ask him if he had stopped listening to new music. He had. He grinned.
Before I retired, I worked with a group of young engineers. More than half of them were young enough to be my kids. Yeah, that was a sobering moment…
And I wholeheartedly agree with quiltguy!!! 
When you pass “the get off my lawn” stage and reach “I don’t give a shit about that lawn” stage. Which is shortly followed by a move to Dell Bocca Vista Phase II.
You know your getting old when your doctor says the CAT scans show significant wear to the knee joint and you have a partial tear to a ligament, it’s time to consider knee replacement surgery. 
And it’s going to mess with my retirements plans too. :(
When I pay attention to AARP commercials.
I feel old when I notice that people who were vibrant, productive adults when I was a kid are dying off. Politicians, actors, musicians, historical figures. Bummer.
… when you hear about someone less than 15 years older than you (but in their 70s or 80s) dying, and you think: “He/She was so young!!”
On the way to work the other day I was thoroughly enjoying a song from my wild college days and when the song ended, I realized that I was listening to our local oldies station.
You Know You’re Getting Old When: You keep a pair of reading glasses in (most) every room of the house.
In this vein… when I heard “Black Hole Sun” on the oldies station.