I’m still in my 20s, but as of a few years ago I started forgetting what’s my exact age. I always have to stop and recalculate it each time someone asks me. I get asked fairly infrequently, but when I do it’s a bit weird/embarrassing that I have to say “wait, let me calculate”. (I know when I was born, of course.)
It seems as if there’s no good reason I’d remember it, since it changes all the time and it is rarely mentioned in practice. But others, including people much older than myself, know their own age immediately.
I’m also terrible at remembering people’s names, I don’t know if that could be related?
I usually have to stop and think about it, not recalculate it but it takes a few seconds for the query to run.
I’m not big on celebrating my birthday, I just kind of check off some milestones
Old enough to drive, vote, drink, rent a car, run for president (not quite there yet, look for me on the 2028 ballot though) get an AARP membership, retire, and then that’s pretty much it, then I’ll coast the last couple of decades of my life no longer needing to know how old I am.