You know you're old when...

you're on the committee for the 20 year high school reunion, and the reunion is more than a year away.
you realize you're closer to your 50s than your 20s.
you fear jumping off the swing or jungle gym while at the park with your kid because you're afraid you might break a hip.
you do jump off the jungle gym and your body feels out of whack for a week.
you realize you're not immortal.
you relish the mid-afternoon cat nap.
you can't recall if you knew someone from high school or college.
you can't tell the difference between high school and college kids.
you were so excited to buy a Volvo because of safety.
you are considering getting rid of your vacuum and buying the sleeker Dyson, mostly because it's easy to clean.
you stay up late at night finishing a good book instead of hitting the bars.
you don't call anyone and no one calls you after 8 so as not to wake up the kids.
you have to explain to your kid what a tape cassette or record is.
you tell your kid to "eat his vegetables".
you save money for your retirement instead of a car or "stereo".
you look at teenagers and say, "What the hell are they wearing?" Then you realize that 80s styles are back in style, or was that 90s?
you hear a familiar song on the radio and realize that it's part of "flashback" weekend.
you and all your friends constantly talk about the pros and cons of public vs. private schools.
you hear yourself arguing with your kid, "No, this IS cool. Mommy knows what's cool." [cringe!!]
you crave a nice quiet evening at home, curled up with a book and hot cocoa or tea.
you spend more money on dinner than drinks.
you think, "How easy will this be to clean?" when weighing whether or not to buy something.
you pick up something kind of racy while out shopping, but put it down because you think, "When would I actually wear this?"
your Scrabble opponent on Facebook (who's a college senior) lets you know "you sure don't look 37".
you get your butt whooped by that same Scrabble opponent and you imagine him telling his roommates, "I just kicked some old lady's ass in Scrabble!"