Reversed birthdays
“Not everything that counts can be counted, and not everything that can be counted counts.” Albert Einstein (1879–1955), Swiss-American theoretical physicist of German origin
There are some ideas that I feel I’d never come up with myself. I’m all the happier, then, when they just cross my path. This was the case a few days ago. A woman and two men walking behind me were talking about their birthdays. When one of the men gave his, the woman immediately replied. “That’s great, yours is on 3.9. and mine on 9.3. We have reversed birthdays. I was born two months premature, so it’s almost seems as if fate wanted us to have reversed birthdays.”
It was with some regret that I realised that this happiness is only granted to people born up to and including on the 12th of a month, so a majority doesn’t have it at all. Is that actually true? After all, birthdays aren’t evenly distributed throughout the year.
In Germany, for example, more people are born in late summer and early autumn, with September in particular standing out as the month with the highest number of births. This is also the case in most Western countries – more children are conceived in the winter months.
Birthdays that fall during this time, on the other hand, are rarer, especially in February. Holidays such as Christmas and New Year also have low birth rates, as medical procedures are then often postponed to other days. In addition, the latest figures from 2023 show that about 28% more births take place on Mondays to Fridays than at weekends.
In any case, a random sample in my immediate circle of friends showed that out of 30 people, only nine were born in the first twelve days. Of course, this isn’t representative. So I asked Germany’s federal statistical office and compared the births in days 1 to 12 of a month with those in the days 19 to 30 of each month between 2014 and 2023.
The result was that whilst in some years (such as 2021, 2020 and 2019) more babies were born towards the end of the month, in other years (such as 2023 and 2022) there is a slight increase in the first half of the month. So there is no uniform trend over these years.
Mathematically, with an average number of 30.4 days per month in our Gregorian calendar, almost 40% have a birthday in the first twelve days and can celebrate it twice – among them, of course, are also those with double-figured birthdays, some of whom may already have been congratulated twice a year for a long time. Particularly those whose winter birthdays fall on the 4th to 9th day of the month, and who haven’t wanted to celebrate outside due to the weather, but would like to, now have handy alternative dates. Mathematically, however, only just under 9% of people have birthdays on these six days in the cold half of the year.
Unless, of course, there are other calendars. And indeed, in Ethiopia it is 13 months, twelve months with 30 days and an additional short month with five or six days, depending on the leap year. So that means that, mathematically, 1.4% more people than in this country can celebrate their reverse birthdays there in a normal year.
On the other hand, who says that you can only celebrate on one or maximum two days? Recently, during a train ride, I got into a conversation with a woman who said she was 57½ today. So why not celebrate your half-birthday, or even create another occasion for yourself? Then you can enjoy more cakes and more flowers!
Anyway – every day is a good day for a celebration!