I’m the other way around. Only people born before the year 2000 can be adults. Everyone born afterwards is permanently a child and shouldn’t be left alone without a babysitter.
I actually struggle with the same mental image. Anybody born after 2000 still goes to school in my mind.
I can't describe the reaction I always have inside when I consciously realize that post-2000 kids can actually be adults. Not just because I realize how screwed my perception of time is but also because I suddenly feel old.
We do happen to be roughly a quarter of the way towards the next century, so this seems reasonable to me. Longer lived Gen Z will likely be able to see the turn of the 22nd century, after all.
Then you have communities like unpopular opinion that have you voting backwards. You really have to be paying attention to get it right. It’s not easy when you factor in all these things.