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Why is Friday the 13th considered unlucky? There's always at least one Friday the 13th every year, sometimes as many as three. And that is the case for 2026. It costs the United States economy apparently hundreds of millions each time, as people cancel flights, avoid business deals, skip travel. And you'd be forgiven for thinking this superstition might be ancient. It isn't. Well, at least not in the way that most people might think. So where does it come from? And why do otherwise rational people still feel afflicted liquor of unease when they see it on the calendar? Let's start with the number, because 13 has a complicated history. So, in Christian tradition, the last supper had 13 people at the table. Jesus plus the 12 disciples. Judas the betrayer is often described as the 13th guest. And then the crucifixion follows the next day on a Friday. More on that in a moment. However, medieval Christians didn't universally treat 13 as curse, because, in fact, symbolically emulating the Last Supper could be considered meaningful rather than purely ominous. There are European mythological stories, too. In Norse mythology, 12 gods are dining in Valhalla when Loki the trickster arrives uninvited as the 13th guest. And then chaos ensues. But again, there's no evidence that medieval Scandinavians went around actually fearing the number 13 in daily life. This connection appears to be retrospective. So as soon as 13 became unlucky, then you find matches for that in earlier traditions. The idea of 13 as inherently unlucky becomes more visible in Europe around the 17th century. And actually, I was going through some documents from witchcraft trials from the 1600s in Scotland mainly. And these poor people who are being forced to confess under duress frequently cite that there are 13 members of a witch's coven. So it's likely that by the late 1600s, there is this association between 13 and witchcraft, Satan in public consciousness. There's also a more fundamental theory about why humans don't like 13, and that's our need for order, because 12 is mathematically stable. 12 months, 12 zodiac signs, 12 inches in a foot, it's neat. But 13 disrupts symmetry. It's a prime number, so it's indivisible apart from itself and 1. And culturally, 12 feels quite complete, whereas 13 feels like a bit of a hangover. And as someone who used to have OCD as a kid, I very much relate to this feeling of, like, unfinished business on the 13. Anthropologists might call this weirdness around Friday the 13th a kind of cultural survival, which was a concept introduced by Edward Burnet tylor in the 19th century, this is the notion that a belief outlives its original conditions, but lingers detached from the initial meaning or superstition. But it still does something to us emotionally when we think about it. And it does linger, because today hotel rooms skip room 13 often. High rise buildings sometimes jump from floors 12 to 14. Airlines can emit row 13. So even if, as a society, we say we don't believe in this, we definitely hedge now back to the Friday component. Specifically, in medieval Europe, Friday was considered an inauspicious day. It was the day of Christ's crucifixion. Good Friday. Geoffrey Chaucer, father of English poetry, warned about the fifth day of the week back in the 14th century. So in the Canterbury Tales, he writes that Friday is an unlucky day. He mentions that on a Friday fell, all this mischance, which indicates that at least in English culture at that time, Friday has some kind of shadow around it long before it meets 13 in this combination. And that combination together doesn't clearly appear in print until the 19th century. Actually, so very late in 1834, an article in a French literary magazine, Review du Paris, remarks, it is always Fridays and the number 13 that bring bad luck. So clear as day, there is the association. And there's a French play the same year, Les Finesse des Griboules, which says the same. By the way, if you're kind enough to be invested in the show and watching it, I will tell you right now that my French accent is appalling and I always sound like Borat. So let's just accept that at this juncture in this French play, there is a character that laments being born on Friday the 13th. And that character says, I was born on a Friday, Dec. 13, 1813, from which comes all my misfortunes. References in the English speaking world become much more common in the early 20th century. Folklorists at the Library of Congress note that the first clear American print references appear around 1913. Interestingly, so definitely not an ancient curse or superstition. And you may or may not have heard about this tangential connection between Friday the 13th and the Knights Templar. The Knights Templar, which is a posthumously prolific organisation that are implausibly tacked on to almost every historical oddity that there is. Anyway, on Friday, October 13, 1307, King Philip IV of France arrests hundreds of Knights Templar and many were tortured and later executed, and the Grand Master was burned at the stake. So very dramatic and traumatic. And that's been put forward as a possible origin of the superstition but there's no contemporary evidence that medieval Europeans at the time made that link. That association appears much later now. The psychology of it all. There is a name for the fear of Friday the 13th, and it is paraskevidekatriophobia, from the Greek Paraskevi Friday, Triska Decker, 13 and Phobos fear. Psychotherapist Donald Dossey popularized the term in the 20th century. For some people, this anxiety is very real. So why do humans experience this? Folklorists argue that superstition gives us the illusion of control in a chaotic world. If something bad happens on Friday the 13th, it confirms that story for us. And if nothing happens, we just forget about it. So basic confirmation bias. Human beings like patterns, especially when the alternative is an abyss of uncertainty. We find meaning where none might exist. It's just cognitively safer to assume patterns that we can prepare for instead of utter randomness. And once a belief becomes socially shared, it reinforces itself. There's even data that suggests this. Because of the reduced air travel, fewer financial transactions, postponed surgeries, the superstition of Friday the 13th creates an economic footprint. There's a professor called Richard Wiseman who pioneered the Luck project. And he argues that what we call luck is the downstream result of our attention, behavior and interpretation, not a mysterious force. He studied hundreds of self identified, lucky and unlucky people and found what is probably very obvious, that those who describe themselves as lucky tend to create and notice chance opportunities more readily. They vary their routines, they're more likely to speak to new people, and they remain open to new information and experiences. They also trust their intuition more and expect positive outcomes, which increases the likelihood of of self fulfilling effects. By contrast, those who consider themselves unlucky are generally more anxious and threat focused, which can narrow attention and cause them to miss opportunities that are plainly visible. And on a culturally loaded date like Friday the 13th, if you're all funny about it, your brain's reticular activating system is searching for weirdness and danger and then confirmation bias does the rest. So you notice you spilled your coffee, there was a delay, there was a weird email, and you encode it as evidence. So it's selective attention expectation, anxiety driven error, even. That's the engine behind it. But interestingly, one of the journal articles that I read when I was researching this, called the Empirics of bad Luck, actually noted in their footnotes. I do read all the footnotes that the initial version of the present paper counted exactly 13 pages, single spaced, and it was rejected by five journals. The next version was 16 pages and was accepted with very minor changes. Friday the 13th is not universally unlucky, though. In Islam, Friday is the holiest day of the week, a day of congregational prayer. And there's no inherent stigma attached to the 13th. In Judaism, Friday evening marks the beginning of Shabbat. And the number 13 can have positive associations like Bar Mitzvah at 13. There are 13 attributes of mercy in Jewish tradition. In Spain and Greece, the unlucky day is not Friday the 13th. It is Tuesday the 13th because Tuesday is associated with Mars, the God of war in Spanish. In Italy, the feared date is Friday the 17th because the Roman numeral for 17 can be rearranged to spell death. Or I have lived more precisely in Japan and China. The number four is often avoided because it sounds like the word for death. I'm taking academics word for it because I don't speak those languages. The fourth day of the fourth month can carry cultural anxiety. So all of these things tell us something important, that unlucky days are obviously culturally constructive. They cluster around linguistic, religious and symbolic meanings which chime in some way with our existential fears. And Friday the 13th happens to be the western one, which is exported globally through media, especially 20th century horror franchises that turn that date into a dramatic one for cinema and doom. Now, because of our pattern seeking, strange events do get attached to Friday the 13th. Large scale analyses show no consistent spikes, spike in accidents or disasters on these unlucky days. Unfortunately, there are just multitudes of bad and good things happening at all times and that can confirm superstitions around any date. So Friday the 13th is definitely not an ancient superstition. It is not traceable directly to the Knights Templar, nor is it universally feared. It appears to be a relatively modern fusion of two older nebulous superstitions, an unease around the number 13, especially in Western Christian tradition, and, and some sort of shadowy concern around Fridays. And these superstitions survive because sometimes randomness just feels psychologically intolerable. If we can find a pattern and we can name it, if we can give chaos a calendar, that's quite therapeutic for us humans because it implies that there's something about events that's not arbitrary and is arranged. And that impulse to believe that there's order beneath the accident is the same impulse that we look for in myth, in religion, and in all the things that we search for as humans. So I'm not going to scoff at people that are worried about it because actually I think it makes sense. I can see where it comes from. How about you Is this something that freaks you out? Do you think it's an absurd irrationality? Let me know in the comments and I will see you next time.