Date-related buggery-bollocks

A couple of years ago, some idiot proclaimed that October 2010 was the first month in 100 years that contained five Fridays, five Saturdays and five Sundays. Everyone swooned.

A few months later, people swooned similarly at proclamations that January 2011 contained five Saturdays, Sundays and Mondays.

It was all bollocks, of course.

And yesterday, The Illuminati (spoof account) tweeted:

Friday the 13th occurs 3 times this year, each 13 weeks apart from the other. This won’t happen again for 666 years. Happy Friday the 13th.

The numbers made the assertion more believable. But some relatively basic analysis proved it not to be the case. But that didn’t stop 12,900 people retweeting the “fact”, nor 2,132 people adding it as a favourite.

The initial sentence is correct. There were indeed three Friday 13ths this year. And occurring in January, April and July, they were 13 weeks apart from one another.

But its rarity is overstated.

In 2678, 666 years from now, there will be only two Friday 13ths, in September and December. They will indeed be 13 weeks apart, but there are years long before then sharing in that property. 2018 will also have two, 13 weeks apart, in April and July.

If you’re looking for the next year with three, 13 weeks apart, then that will occur in 28 years, in 2040: January, April and July again.

With Twitter, it’s much easier to accept and swoon (and retweet) than to query.

(Thanks to Alan for questioning the original post.)

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