Friday the 13th Superstitions Rooted in Bible and More
This year Friday the 13th superstitions get a break—luckily for triskaidekaphobes.
That must come as a relief, after 2009's three Friday the 13ths—the maximum possible in a year, at least as long as we continue to mark time with the Gregorian calendar, which Pope Gregory XIII ordered the Catholic Church to adopt in 1582.
"You can't have any [years] with none, and you can't have any with four, because of our funny calendar," said Underwood Dudley, a professor emeritus of mathematics at DePauw University in Indiana, and author of Numerology: Or, What Pythagoras Wrought.
The calendar works just as its predecessor, the Julian calendar, did, with a leap year every four years. But the Gregorian calendar skips leap years on century years except those divisible by 400. For example, there was no
