What was your "oh god, I'm old" moment?

Going to a club, security guy checking id for date of birth and then staring at me with incomprehension. Don’t think he’d seen a year that far back.

Every time I think back to something that happened "recently" only to realize it was 10+ years ago.
- I do that sometimes and im in my early 20s if it makes you feel any better. My sense of time was broken from covid though.

When I ran into a kid I had babysat as a teenager, and the dude was all mustachioed and bearded. Kid was a toddler when I sat for him the first time.
I run into him like that at my old high school. Dude was teaching there.
- At one point I substitute taught high school and a kid I babysat was in the class.

When I called my cousin to wish her happy 18th bday and I remembered she used to fall asleep on my belly as a toddler.

Literally yesterday. On a beach and see this guy watch his dog take a dump and then walk away. I'm not having that. So... ask if he needs a poop bag and he gets up in my face waving his own poop bag asking if "I know what this is for?" I replied "obviously not for picking up your dog's poop in a timely manner" and things devolved from there ultimately ending with him yelling at me to "Shut the fuck up and mind my own business old man." I picked the poop he was responsible for and today my back hurts a bit.

I was buying beer at one of those places where the cashier had to input your birthdate into the register. The cashier said "Oops, I put a 9 instead of an 8", and then handed me my beer. Suddenly realizing I could drink legally for over a decade made me feel old.
Edit: Now I'm realizing that this story is more than a decade old...
- I finally stopped getting carded a few years ago (I'm 45). Now cashiers will just enter a random date... one person chose to put my birthdate as 1962.
  
  If it makes you feel better, some stores have a policy not to ID people over 65, so cashiers just put people's age as 65 when they don't want to bother to card someone.

I first noticed my body was aging when I jumped off a dock to go run forward and see if I could see the truck. It was something I often did. Not unusual at all. One day I did it and after landing I just stopped. Because I really felt it. It was no longer a nothing thing I would do casually. It was followed by many. Many more bodily awakenings.

The day I realized how dangerous showering in a tub is if you were to slip and fall.
- It's the difference between falling and having a fall....

In my 30s I lived in China as an English teacher. Walking through the school to my apartment I passed two 10 year olds playing who stood up as I approached and bowed, saying "Hello grandfather".
Just a couple of weeks ago a co-worker in his 20s said I have "dad vibes". I am a dad, but still! 😡

Random kid greeted me like I used to greet old people.
- You used to have a special greeting for old people?
  
  Formal/informal. Most languages have that kind of separation. In English it would be something like the difference between "Hello" and "Sup fuckface".

I live pretty urban. In the last years I've been going from not caring or chuckling about the weekendly drunkards outside my window to catching myself looking grumpily at the clock and cursing to myself.
For context, I am only mid thirties and most of the time still awake myself when that happens so I have zero rational excuse.

The first time the Playboy Playmate of the Month was younger than me was kind of a weird moment.

One of my most loved punk song since my late teens/early twenties just got a 20th anniversary re-recording.

My boss joked that when you pass a certain age it's not your left and right knee, but the bad one and the not so bad one.
And I realized, damn it, he's right.

First time was long ago now, but I remember a guy holding a door open for me and calling me 'sir'.

Hmm... I don't like these new cars with their touchscreens. I'll just wait a few years for that fad to go away. Said me, around 2007.

People wearing band shirts of stuff I grew up listening to and realizing they’re younger than when those bands existed. That and hearing the same music played at the grocery store realizing it’s now so old it’s cheap royalty music.

Realizing that most kids who saw Illumination's Mario movie think it's the first Mario movie.