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?
Totally normal. 21 was your last milestone, 22 was your first year of “I’m older than 21.” Everything after that will be fuzzy except for the decade milestones and maybe the half decade ones.
I’m not American, so not even that, actually. I guess 20 was sort of a milestone, but only symbolically, entering my third decade of life…