Common Mysteries: case file #002- Why is Friday the 13th considered unlucky?
- Avni Koppula
- 5 days ago
- 3 min read
Case Opened: October 2025
Subject: The Origins of the Unluckiest Day
Setting the Scene
Every year the calendar hits that date- Friday the 13th- and suddenly everyone's a little more cautious. Elevators skip the 13th floor, airlines avoid the row, and horror franchises cash in on superstition. But where did this fear come from? Let’s reopen the file.
Exhibit A: The Number 13
Across cultures, the number 12 symbolizes peace and order- twelve months, twelve zodiac signs, twelve apostles, twelve Olympians. But 13? Uneven. That unease even has a name- triskaidekaphobia, the fear of the number 13 (MedicalNewsToday).
Some historians trace this back to Norse mythology, where Loki crashed a banquet in Valhalla as the 13th guest. This trick then led to the death of Balder (the God of joy and light), throwing the world into darkness and mourning (Norwegian American).
In Christian tradition, Judas (the disciple who betrays Jesus), was the 13th guest at the last supper (Library of Congress).
So it seems that at many tables, 13 has long been the outsider number.
Exhibit B: Fridays
Before it became the start of the weekend, Friday was a day people avoided, for important beginnings. In medieval Europe, ships hesitated to leave on Fridays for the belief that it would bring bad luck. Religious beliefs also deepen the superstition: Christians observe that Jesus was crucified on a Friday, and also connect it to the biblical “Friday Fall” of Adam and Eve (History.com).
By the time our modern calendar came about, both the number 13 and Friday had already developed separate bad reputations, I guess it was only a matter of time before they teamed up.
Exhibit C: The Superstition is Born
The specific fear of Friday the 13th as a single unit didn’t really appear until the 19th century. One of the earliest written mentions of it comes from the biography of a composer named Gioachino Rossini, who self reportedly feared both Fridays and the number 13 (IBT).
But things only really started kicking off after Thomas W. Lawson wrote his novel Friday the 13th (1907), which talked about a broker who used superstition to manipulate Wall Street.
Pop culture sealed the deal in 1980 with the release of our favorite horror classic, Friday the 13th, which truly transformed the date into a cinematic symbol of bad luck and masked murderers.
Exhibit D: The Modern Day Curse
Even though all of this seems just a little silly, superstition still proves to have a very big impact. Economists estimate that a crazy $700-$900 million is lost in sales every Friday the 13th, as people don’t book trips, meetings, and don't make any significant purchases (GoBanking).
Yet, studies show that accidents and deaths don't really increase on that day at all (British Medical Journal). If anything, the fear itself can cause stress, distraction, and maybe a few minor mishaps- like a kind of self-fulfilling prophecy. In other words, it’s not that Friday the 13th is unlucky, it's that people believe it is.
Case Closed?
Collective storytelling is a powerful thing. A feared number, a dreaded day, almost a century of retelling to create a superstition strong enough to change behavior, even now. So I guess the next time the calendar creeps up on that fateful day, just remember luck isn’t written in the stars- it's written in your head.
Filed under: Cultural Superstitions, Psychological Mysteries