I was buying beer at one of those places where the cashier had to input your birthdate into the register. The cashier said "Oops, I put a 9 instead of an 8", and then handed me my beer. Suddenly realizing I could drink legally for over a decade made me feel old.
Edit: Now I'm realizing that this story is more than a decade old...
If it makes you feel better, some stores have a policy not to ID people over 65, so cashiers just put people's age as 65 when they don't want to bother to card someone.