I keep a list of people that are famous-to-me that are old so that if someone dies I won't be surprised. When Lauren Bacall died recently I (1) knew who she was, AND (2) knew she wasn't already dead. I DO NOT look at lists of celebs. My list is organic- if I think of someone who seems old (`GEE, I wonder if that famous probabilist Monty Hall is still alive? He is! He's 92.) I look it up and if they are over 80, they go on the list. Most people are surprised to know that Dorris Day is still alive.
Okay, so what of it? Bill has another weird hobby. (Add this to collecting satires, collecting papers that apply Ramsey Theory, and writing a satire of papers that apply Ramsey theory).
I decided to see how many people on my list had the same birthday and see if it was reasonable with regard to probability (the birthday paradox and all that). The list currently has 70 people.
What I found was probably reasonable in one respect and odd in another.
REASONABLE: Nine pairs had the same birthday. One triple had the same birthday.
ODD: There were NO pairs or triples of same birthdays in July, September, October, November, or December.
I leave as an exercise: How reasonable is what I called reasonable and how odd is what I called odd?