I Don't Know How Old I Am

Back when I was 21, I could tell you my age when asked. These days I have to sit back and do a calculation based on my birth date. I guess there's nothing special until I hit 30. I'll probably be able to know my age again at least when I am 30. I just don't think it's quite as important anymore. Maybe a year makes a difference on one of those max heart rate calculations or something, but not socially and not practically. Who cares how old I am?