It was 5:20 a.m. and I was finishing my second cup of coffee when it dawned on me – the question:
How many birthdays have I had on the same day of the week as my date of birth?
In resolution, using this weekday calendar, I laboriously set about to record the years in which I had a birthday on the Sabbath, being born on a Sunday.
Granted, this number of same days of the week may be of minimal interest, yet I did observe a pattern. So, I checked a few other sample birthdates to substantiate the following conclusion:
With the exception of February 29th, every birthdate, on any given day of the week, recurs on that day of the week in accordance with the following pattern of years…
↱ 6 · 11 · 6 · 5 ↲
So, if your birthday on the same day of the week as your date of birth initially occurs at age 11, it then recurs at intervals of 6, 5, 6 and 11 years, as a repeating loop.
Also, if by chance you happened to be born in a leap year on February 29th, your next calendar birthday of February 29th – on the same day of the week as your birthdate – will occur in a cycle every 28 years.
You may say that I’ve got too much time on my hands, but cut me some slack – and cake – as today is my birthday. Happy birthday, me!