Thanks everyone. The story behind the disagreement is pretty boring.
We were talking about our son, who is 28, unmarried, and at the moment has no girlfriend (though he has had a couple of long-term relationships in the past). He is a snuggly guy and would love a permanent relationship. (Why he isn’t in one is a subject for another day, or thread.*)
I said something along the lines of “I wouldn’t want CairoSon to be depressed because he is 28 and single, and his parents got married at ages 23 and 25.” At which point Mr. Cairo says, “oh no, we were married at 24 and 26.” (In fact, with a few changes to make the example simpler/starker, we were married as described in the OP.)
Mr. Cairo always rounds up everything. Which makes sense in some situations, but I don’t know why the hell you’d round up your age. My argument to him was: Look, you will be age X for 12 months no matter what. If you start using a rounding rule, you’ll just state your age for a slightly shifted 12-month period.
So why not count like people generally count people’s ages? If you die in a car crash when you are 48 years and 11 months old, the newspaper article about the crash is not going to ID you as 49. It will say you were 48.
Mr. Cairo’s response was, “well, but that’s how most people do it” (meaning everyone rounds up). I disagreed, claiming most people (Americans, anyway) do NOT round up. According to me, the American standard is this: when you are 53 years, 11 months, and 27 days old, you are 53. You turn 54 ON YOUR BIRTHDAY.
He eventually conceded that he wasn’t really sure how most people characterize their age, so agreed to having me ask Dopers, in case he was wrong and his rounding up is atypical.
Thank you all for your input. I feel vindicated.
*Any of you with most excellent mental catalogs of Dopers will also wonder about the inconsistency between this thread and what I’m posting here, which is also a long story for another thread. Suffice it to say things changed. All is well in my life now.