Friday the 13th, how rare?

If you hadn’t noticed it’s that dreaded day, Friday 13th again. The day when everything goes wrong.

Thankfully it doesn’t come around that often, or does it? Well, the next one is just 4 weeks away, March 13th to be precise.

That’ll be the last one for a while, won’t it? Er, not really, there’s another by the end of the year.

Considering there are only 12 days a year when the 13th occurs on the calendar, it is admittedly rather unusual to have three instances of Friday 13th in the same calendar year

A year doesn’t go by without at least one Friday 13th, and there are quite often two Friday 13ths, but three don’t come along so much. The next one is 2025.

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4 thoughts on “Friday the 13th, how rare?”

  1. As long as the first day of the month is Sunday, there would be Friday the 13th in that month. Also, Sunday has the highest probability of occurring on the first date of any months. Therefore, it means that Friday has the highest chance to become the 13th day of any months than any other days.

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    1. Many thanks for the comment abyssbrain.
      I must confess I had no idea that Sunday is the most frequent day to land on the first of each month. Maybe you could elaborate how this happens.

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      1. Our calendar has a cycle of 400 yrs. This means that Feb. 13, 1615 and 2415 is also Friday the 13th. A while ago, I’ve run a test on Mathematica (I wasn’t aware at that time that it has been done already) to see how often Sunday occurs on each month in 400 years (4800 months). The result was 688 times wuch is the highest. The lowest are Sat. and Mon. with 684 times. That means that Friday the 13th occurs more often. Granted, the difference from the highest to the lowest is between 14.3% and 14.25%, but still…

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