Fifteen years ago I was married.
"But certainly you aren't old enough to be married 15 years!" you say. Thank you! (just barely, but yes.)
I'd love to tell you that we celebrated with a romantic dinner, or a weekend getaway for two, or something along those lines.
Instead I celebrated by taking the kids to swimming lessons, cleaning out the minivan, taking the kids to a movie, and refereeing exactly 57 arguments. (Only one of which, was really justified.)
He celebrated by rushing to get to the Hong Kong airport on time for his 15(ish) hour flight.
Sadly, many of our anniversaries are celebrated along these lines. (apart, that is.)