Doug’s Seventh Year
Posted by Neal on August 10, 2004
Today is Doug’s sixth birthday. As I tucked him into bed a few hours ago, I congratulated him on beginning his seventh year on the planet. He said, “No, my sixth year.” I said no, his sixth birthday meant he’d finished living six years, just like his first birthday meant he’d finished living one year.
He got the picture, but it was interesting that he got thrown off by hearing the word seventh on his sixth birthday. I used to have the same kind of confusion, only I never even realized I was confused until a couple of years ago, when for no particular reason it occurred to me that when you said that so-and-so accomplished such-and-such in his nth year, it really meant that he did it when he was (n-1) years old.
Or did it? All the time I’d been hearing the phrasing in [someone]’s nth year, I’d kind of translated it as “when they were n years old,” without thinking about it. Maybe everyone else did, too. But would this pattern hold true when n = 1? I think most parents would interpret something like In his first year, Johnny learned to crawl, got 2 teeth, and said “Mama” and “Dada” to mean that he did these things before his first birthday, not after it, when he was one year old. In that case, I have the same kind of question as I did regarding one troop vs. 100 troops: for what positive integer j does in one’s jth year mean “when one is (j-1) years old,” while in one’s (j+1)th year means “when one is (j+1) years old”?