The way the calendar falls this year, there are three months in which the 13th day falls on a Friday -- creating three unlucky holidays that have spawned many a horror movie.
This month's is the second in a row -- Feb. 13 also fell on a Friday. And November will include a Friday the 13th, too.
This pattern of February/March/November Friday the 13ths happens periodically, explains EarthSky.org -- in any year that begins on a Thursday. In those years (as long as it's not a leap year), February, March and November all begin on Sundays, which means in each of those months, the 13th day falls on a Friday.
The last time it happened was 2009, and the next time will be in 2026 and then 2037. EarthSky breaks down the patterns in the Gregorian calendar that allow this to happen.
It's not known exactly why Friday the 13th has its spooky reputation.
According to Snopes, "Some of the more common theories link it to a significant event in Christian tradition said to have taken place on Friday, such as the Crucifixion, Eve's offering the apple to Adam in the Garden of Eden, the beginning of the Great Flood, or the confusion at the Tower of Babel." The number 13 is considered ominous perhaps because Judas Iscariot was invited as the 13th guest at the Last Supper before betraying Jesus and leading to his crucifiction.
There is mixed proof on whether it is actually an unlucky day, according to the International Business Times. Some studies have concluded traffic accidents are less likely on Friday the 13th compared to other Fridays, while others have suggested they are more likely.
But fear of the number 13 -- triskaidekaphobia -- and of Friday the 13th -- paraskevidekatriaphobia -- are both real ailments. Two U.S. presidents, Herbert Hoover and Franklin Delano Roosevelt, were both triskaidekaphobic, according to Scientific American.