Friday the 13th has a pretty bad reputation. For most, it signifies a day where you’ll be extra careful around mirrors, watch out for black cats crossing your path, and avoid walking under any ladders that might be lying around. If you’re superstitious already, you’ll be pleased—or, more likely, pretty terrified—to know that this Friday the 13th is about to be extra spooky. And no, it’s not because Jason Voorhees is waiting for you in a hockey mask.

Why don’t you press play and listen to Stevie Wonder’s “Superstition” to put yourself in the mood?

Now that we’ve set the mood, what is so spooky about this month’s most unlucky day? In addition to it being Friday the 13th, it’s also a rare, full Harvest Moon. It has been 19 years since there was a nationwide Harvest Moon, and there won’t be another one until 2049.

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Is that not spooky enough for you? Allow us to explain.

Full moons, Fridays and the number 13 are all notoriously unlucky. Put em’ all together and boy, things are about to get spooky up in here!

What the heck is so bad about Friday the 13th?

It’s easy to assume someone just decided one day that 13 was a bad number and somehow convinced all of their friends to believe it, too, but that’s not exactly the case—I mean, unless you think Hammurabi was just a funny guy who wanted to play a prank when he omitted the number 13 on Babylon’s Code of Hammurabi. That’s how far back this superstition seemingly goes.

The number 13 has been considered unlucky for centuries. Some historians have pointed to the Last Supper as its origin of unluckiness: 13 people attended and two (Jesus and Judas) died. Friday also comes into play in this example because Jesus was crucified on a Friday. While you may know Friday as “OMG, I’m Off of Work, Let’s Get Happy Hour” Day, it’s more commonly known as hangman’s day—and we’re not talking the fun, but mildly inappropriate when you think about it, children’s game.

According to Donald Dossey, a folklore historian and founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina, Friday the 13th is unlucky for businesses too, though it’s kind of a “what came first, the superstition or the egg?” situation: “$800 or $900 million is lost in business on because people will not fly or do business they normally would.”

And though this isn’t particularly spooky, it is interesting timing: this Friday the 13th falls during Palindrome Week, in which every date can be read the same forward as backward (so 9-13-19). Is there anything more ominous than date-related trivia?

Okay, we get it, Friday the 13th is unlucky. What about full moons?

Chances are, you’ve heard someone in your life say, “must be a full moon” when things aren’t quite going their way. This is some science behind this. One study published in Scientific American found that, compared to the rest of the month, people typically do not sleep as soundly during a full moon. A study done at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences suggests that emergency visits for cats and dogs increase when there’s a full moon. If it can happen to cats and dogs, can’t it happen to you?!

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What happens when you don’t get enough sleep? You get cranky! What happens when you get cranky? We’ll tell you what happens: Bad things!

Now, technically East coasters are safe from the extra bad luck—the Harvest Moon won’t arrive until 12:33 a.m., which means it’s actually a full moon on September 14th.

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And with this moon and this Friday the 13th, we officially declare Spooky Season officially here!

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