Okay, I can't remember exactly what prompted this, but I was looking up something about astrological signs. Because the standard dates for a given sign of the Zodiac were set a while ago, and there's been some astronomical drift, your sign by date may not correspond to what constellation was actually in position at the time. (Hermione, ever-correct, was born on one of about four days where she's a Libra no matter how you decide.) On top of that, a thirteenth constellation is actually sitting in the "ring" that the Zodiac ones appear to lie along: Ophiuchus, aka the Snake-Handler, aka (but possibly not for astronomical purposes) Aesclepius, the name under which I was familiar with the guy who got his ears licked clean by snakes as a young man, was thereby granted the ability to hear the speech of animals, and thus became a great healer, learned to raise the dead, and was eventually lightning-struck by Zeus for taking money for it. (In fact, that's why I have for some time written fic under the assumption that there may be healing spells incanted in Parseltongue.)

Anyway, Ophiuchus wouldn't really make for even divisions, but if it's included (and really, with the wizarding world attachment to prime numbers, somebody's got to be doing it, whether it's traditional or only shows up in Quibbler horoscopes), it would rule late November and early December. Alan and I had dropped Tom's birthday in late November for non-astrological reasons.