When I hear people lamenting the fact that they just turned 20, or even 30, and they feel “so old” now, I always feel amused, like a wizened old sage thinking, “you have much to learn...” or something… Anyways, I think it’s pretty rude to be saying stuff like that around people who are older than you are. I’m never the one to bring up the subject of age when I am around my sempai’s, and if the subject does come up, I don’t say things like “you guys are so old”. On the other hand, it is perfectly fine for the older person to say “your still a kid” to someone younger.
Oh, my birthday is coming up and I thought I was going to be 39, but Mariko corrected me and said I was going to be 38. Bay said “whoa”.