Today is Friday 13th. Mind how you go, especially if you believe that unlucky things happen on days like this. If you do attach significance to this date, you may be relieved to find that it is the only time in 2021 that Friday will fall on the 13th day of the month. Next year it will also happen just once, in May.  

Last year it happened twice, as it does most years: in 2020, Friday 13th happened in March and October. In 2019 it happened in September and December, and in 2018 it happened in April and July. The gap between 13 July 2018 and 13 September was as long as the gap can be between successive Friday 13ths: 427 days.  

2026 is the next time when we will have three Friday 13ths in a calendar year, in February, March and October. It didn’t happen in 2020 because it was a leap year. The gap between 13 February and 13 March 2026 will be the shortest possible between successive Friday 13ths, a mere 28 days.  

I am aware of numerous superstitions and generally I do not tempt fate by acting in defiance of them. I would not place a new pair of shoes on the kitchen table (I was aware of that one long before I saw “Blood Brothers”). I do not cut my nails on a Sunday. I try to avoid getting my first glimpse of the crescent moon through glass. I see from this page on timeanddate.com that right now the moon is a “Waxing Crescent” (26.7%). I have not seen it yet in this monthly cycle. How bad will things get if I see it through glass this evening, the only Friday 13th of the year? I don’t plan to find out.