Evidence status: WELL SUPPORTED
Friday can be unlucky.
Thirteen can be unlucky.
Put them together and, according to one of the Western world's best-known superstitions, you have a particularly dangerous date.
Curiously, the combination appears to be considerably younger than either ingredient.
The Short Answer
The specific superstition surrounding Friday the 13th appears to have developed during the nineteenth century from older traditions concerning unlucky Fridays and unlucky thirteen.
Recent Library of Congress research has found clear references in French literature beginning in the 1830s, with the idea becoming recognisable in France by the middle of the nineteenth century and spreading into American popular culture later in the century.
The famous claim that it originated when King Philip IV of France arrested the Knights Templar on Friday, 13 October 1307 is a much later explanation, with no medieval evidence linking that event to the superstition.
What We Know
Friday had an uneasy reputation in Christian European tradition long before it was joined to thirteen.
Christ's crucifixion was commemorated on Good Friday, and Friday became associated with fasting and abstinence. Various strands of European folklore discouraged starting important undertakings on a Friday.
Thirteen had its own separate reputation, particularly around groups of thirteen dining together.
The interesting question is when those two traditions became one.
Library of Congress folklorist Stephen Winick has traced clear French examples to 1834. Later French plays show characters explicitly worrying about undertaking activities on Friday the 13th.
By the late nineteenth century, the belief had reached American newspapers. An 1888 report joked about a baseball club with thirteen players and thirteen directors beginning a trip on Friday the thirteenth. In 1897 a San Antonio newspaper called the combination a “double hoodoo.”
So Friday the 13th is old enough to feel ancient, but the specific combination does not appear to be a medieval superstition.
How It Became a Habit
The combined belief is extremely efficient.
Instead of having to learn a completely new superstition, people merely joined two existing warnings together.
Unlucky day + unlucky number = exceptionally unlucky date.
The calendar then does the marketing.
Every time another Friday the 13th appears, newspapers mention it, people joke about it and the belief gets another burst of cultural oxygen.
A successful 1907 novel by financier Thomas W. Lawson titled Friday, the Thirteenth used the superstition as part of a Wall Street story. Lawson did not invent the belief; his characters already treat it as familiar.
Much later, the Friday the 13th horror-film franchise attached an unforgettable modern image to an already established superstition.
The Story Everyone Tells
The Knights Templar story is almost irresistible.
On Friday, 13 October 1307, King Philip IV of France ordered the arrest of large numbers of Knights Templar.
Members of the order were imprisoned, interrogated and tortured, and the Templars were eventually suppressed.
Because the raid happened on both a Friday and a thirteenth, the story claims that Europeans remembered the day as cursed — and Friday the 13th was born.
It is wonderfully cinematic.
It also appears to be modern metafolklore: a story invented to explain an existing piece of folklore.
What the Evidence Actually Says
Historians have found no medieval tradition connecting the destruction of the Templars with a general fear of Friday the 13th.
For centuries after 1307, there is no trail of Europeans referring to Friday the thirteenth because of the Templar arrests.
The specific superstition becomes visible much later — especially in nineteenth-century France.
So the evidence points towards gradual combination rather than one dramatic medieval event:
DOCUMENTED: Friday already carried negative associations in Christian European culture.
DOCUMENTED: Thirteen had a separate unlucky reputation.
DOCUMENTED: Clear Friday-the-13th references appear in nineteenth-century French sources.
FOLKLORE: The Knights Templar arrest has not been shown to have created the superstition.
WELL SUPPORTED: Friday the 13th developed by combining two older traditions of unlucky day and unlucky number.
Different Elsewhere
The supposed danger is not universal.
In Spain and Greece, Tuesday the 13th traditionally fills a similar role.
Italy has historically regarded Friday the 17th with greater suspicion. One explanation concerns the Roman numeral XVII, which can be rearranged as VIXI, Latin for “I have lived” — implying that life is over.
So even cultures that believe in unlucky dates disagree about which date deserves the honour.
Why It Stuck
Friday the 13th has something most folk beliefs lack:
a recurring appointment.
The calendar brings it back without anybody having to remember when to revive it.
Every few months or years, there it is again.
The superstition essentially renews itself.
Related Curiosities
Why Is the Number 13 Considered Unlucky?
Why Are Black Cats Considered Unlucky?
Why Does Breaking a Mirror Mean Seven Years of Bad Luck?
Why Is Opening an Umbrella Indoors Considered Bad Luck?
Sources & Further Reading
Library of Congress, Folklife Today — Stephen Winick's detailed research into the nineteenth-century development of Friday the 13th and its later metafolklore.
National Geographic — cultural variations in unlucky dates and numbers.
https://www.nationalgeographic.com/science/article/what-is-friday-13th-superstition-facts-science
Smithsonian Magazine — historical background to the number thirteen.
https://www.smithsonianmag.com/arts-culture/five-men-who-hated-or-loved-the-number-13-66940720/
Last checked: 19 September 2026