Birthday season
I've got seven nieces and nephews, the niblings. For the first six their birthdays are all within six weeks of each other. There are five days in which they are all consecutive ages, ie one year they were aged 1, 2, 3, 4, 5, 6. Number seven extended the birthday window by another five weeks and the age range by two years. So this year, within eleven weeks, everyone bumps up to 2, 4, 5, 6, 7, 9, 9.
A while ago I saw a cute third birthday card and bought it. None of them are turning three. I looked at it when I got home. Just must have lost my mind a bit. Assumed someone must be three.
Within this time frame it's also my sister's birthday. And some other people's birthdays. I think at one point last year I was at a birthday party eight out of nine weekends.
It's a good opportunity for the birthday problem. I don't know that many people, and the birth dates of even less, but I still know three pairs who share the same birthday. The birthday problem, I think, plays on our vision of ourselves as centre of the universe. Most of us default to a statistic of the likelihood of someone sharing a birthday with us and not with each other.
A slight issue is that birthdays aren't equally distributed. In the UK the most common birthday is 26th September.
8 of the top 10 dates of birth were towards the end of September – with the other 2 being early October. If births were evenly distributed throughout the year we would expect on average 1,800 births each day. But the average number of births on September 26 was around 2,000.
A fun one for the awkward adult chat at all these kid's birthday parties.