Friday the 13th: Why is it unlucky? Friday the 13th Better stay indoors, folks. It’s Friday 13th, the most cursed day in the calendar. But where did we get the idea that it’s a date when terrible things happen? Friday the 13th is surely just a myth, right? Let’s take a look at the evidence. The clocks are going back, so why are we still losing up to 40 minutes a day?