Friday The 13th

Stupid Question ™
Aug. 12, 1999
By John Ruch
© 1999

Q: What is the origin of Friday the 13th, and why is it Tuesday the 13th in Mexico?
—Geoff Glass


A: The notion that these dates are unlucky is an apparently recent joining of separate superstitions about Friday (or Tuesday) and the number 13.

Some forms of numerology consider 13 lucky, others unlucky. Nobody knows the exact origin of any such tradition.

But the unlucky-13 superstition has nothing to do with witch covens, Norse mythology and/or the highest number to which early humans could count, as some sources say.

The idea certainly predates Christianity, but our modern version was defined by the Biblical Last Supper, in which Jesus and the 11 good disciples were joined by the traitorous Judas to make 13—bad luck for Jesus, who wound up on the cross the next day. This led directly to a superstition that it’s unlucky to have 13 people at a dinner table.

Friday was also considered unlucky from at least the 1300s to the early 1900s. This is also almost certainly a Christian superstition based on Jesus being crucified on a Friday. It was deemed bad luck to start any sort of journey or venture on a Friday. There was even supporting folklore that the British navy tried to debunk this by launching a ship called “Friday” on a Friday, only to have it disappear at sea.

Folklore sources from 100 years ago, and even as late as the 1930s, describe Friday and number-13 superstitions separately, never saying anything about “Friday the 13th.” The earliest citation I could find for a “Friday the 13th” superstition dates to—get this—1913.

It seems natural that an unlucky day with an unlucky number would be considered super-unlucky. But exactly how Friday the 13th became popular, and how the Friday-only superstition faded, seems lost to history. Some suggest the link is the Last Supper, held on a Thursday, was technically on a Friday since the Jewish day begins at sundown—a contortion that fails to explain why Friday and 13 remained independently unlucky for 1,900 years.
In Spain and Latin America, Tuesday was also independently unlucky. There are many cautionary folk phrases in Mexico, such as, “En martes ni te cases ni te embarques, ni de tu cases te separes” (“Don’t get married, go on a trip or stray far from home on a Tuesday”).

Some suggest this dates to the 1200s, when a now-obscure Spanish king was defeated by the Moors on a Tuesday. But the superstition probably is linked to the Spanish name for Tuesday. Martes derives from Mars, the Roman war god, associated in folk tradition with death.

The number 13 also is independently unlucky in Latin American folklore, and it also hooked up with Tuesday recently and mysteriously. Friday the 13th has been popularized in Latin America due to the US horror film series of the same name; this may have inspired Tuesday the 13th as well.