Friday the 13th is considered unlucky because it combines two long-standing, separate superstitions: the unluckiness of the number 13 and the unluckiness of Fridays. While both have ancient roots, historians believe they only merged into a single “super-superstition” around the 19th century.
Biblical & Religious Origins
The most cited origin is the Last Supper, where 13 people (Jesus and his 12 apostles) sat at a table the night before Jesus’s crucifixion on a Friday.
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The 13th Guest: Judas Iscariot, who betrayed Jesus, is often identified as the 13th guest to arrive.
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Crucifixion Friday: Since Jesus was crucified on a Friday, the day itself became associated with sorrow and misfortune in Christian tradition.
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Other Biblical Events: Some traditions suggest Friday was also the day Eve gave Adam the forbidden apple, Cain killed Abel, and the Great Flood began.
Norse Mythology
A similar “13th guest” myth appears in Norse lore. At a banquet in Valhalla for 12 gods, the trickster god Loki arrived uninvited as the 13th guest and arranged for the beloved god Balder to be killed, plunging the world into darkness.
Mathematical and Cultural Factors
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12 vs. 13: In many cultures, 12 is seen as the number of “completeness” (12 months, 12 zodiac signs, 12 hours on a clock, 12 tribes of Israel). Because 13 follows this “perfect” number, it is often viewed as irregular or unsettling.
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Knights Templar: On Friday, October 13, 1307, King Philip IV of France ordered the mass arrest of the Knights Templar. While some believe this is the true origin, historians note this connection was likely popularized much later by books like The Da Vinci Code.
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Modern Media: The superstition was further cemented by Thomas W. Lawson’s 1907 novel Friday, the Thirteenth and the popular Friday the 13th horror film franchise.
Fast Facts
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Phobia Names: The fear of the number 13 is triskaidekaphobia, while the fear of Friday the 13th is paraskevidekatriaphobia or friggatriskaidekaphobia.
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Cultural Variations: In Italy, Friday the 17th is considered the unluckiest day, while in Spanish-speaking countries and Greece, Tuesday the 13th is the day to avoid.
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Common Behaviors: To avoid “bad luck,” many buildings skip the 13th floor, and some airlines omit row 13.
