Friday the 13th is a Western civilization superstition. The 13th falls on a Friday, at least, once every year on the Gregorian calendar, but it can happen up to three times in year. 2024 had two Friday the 13th. “For example, 2015 had a Friday the 13th in February, March, and November, which will happen again in 2026. Leap years that begin on Sunday (i.e. that follow Dominical Letter AG) such as 2012 and 2040, also have three Friday the 13ths in January, April, and July. 2017 through 2020 had two Friday the 13ths, as did 2023; 2016, 2021, and 2022 had just one Friday the 13th, as will 2025, 2027, and 2028; 2024 will have two Friday the 13ths.” [“Months and years having Friday the 13th”. Time and Date (timeanddate.com).

NOTE: A month has a Friday the 13th if and only if it begins on a Sunday.

History.com tells us, “While Western cultures have historically associated the number 12 with completeness (there are 12 days of Christmas, 12 months and zodiac signs, 12 labors of Hercules, 12 gods of Olympus and 12 tribes of Israel, just to name a few examples), its successor 13 has a long history as a sign of bad luck.

“The ancient Code of Hammurabi, for example, reportedly omitted a 13th law from its list of legal rules. Though this was probably a clerical error, superstitious people sometimes point to this as proof of 13’s longstanding negative associations.

“Fear of the number 13 has even earned a psychological term: triskaidekaphobia.

“13 Is Only Unlucky in the West

“It also seems as if unexplained fears surrounding the number 13 are a primarily Western construct. Some cultures, including the Ancient Egyptians, actually considered the number lucky, while others have simply swapped numbers as the base of their phobias—4 is avoided in much of Asia, for example. 

“According to the Stress Management Center and Phobia Institute in Asheville, North Carolina, more than 80 percent of hi-rise buildings in the United States do not have a 13th floor, and the vast majority of hotels, hospitals and airports avoid using the number for rooms and gates as well. 

“But in much of East and Southeast Asia, where tetraphobia is the norm, you’d be hard-pressed to find much use of the number 4 in private or public life, thanks to similar sounds for the Chinese language (and Chinese-influenced linguistic sub-groups) words for ‘four’ and ‘death.'”

Many believe the number 13 as a sign of doom and gloom comes to us from a Norse myth about twelve gods having supper together in Valhalla, a majestic hall located in Asgard and presided over by the god Odin. Half of those who die in combat enter Valhalla, while the other half are chosen by the goddess Freyja to reside in Fólkvangr. 

The trickster god Loki, who was not invited, arrived as the thirteenth guest, and arranged for Höðr, the god of darkness, to shoot Balder, the god of joy and gladness, with a mistletoe-tipped arrow. Balder died, triggering much suffering in the world, which caused the number 13 to be considered unlucky. [Yes, before you ask, this is the same Thor and Loki from the Marvel Universe.]

Meanwhile, many Christians associate the “evil” of the number 13 with the story of Jesus and the Last Supper. There were 13 individuals present in the Upper Room on the thirteenth of Nisan (the first month of spring) Maundy Thursday 9or Holy Thursday, among other names, is the day during Holy Week that commemorates the Washing of the Feet, the night before the Jesus’s death on Good Friday.

As to the evilness of “Friday,” while there is evidence of both Friday and the number 13 being considered unlucky, there is no record of the two items being referred to as especially unlucky in conjunction before the 19th century.

The Knights Templar

The arrest of the Knights Templar on Friday, October 13, 1307, by officers of King Philip IV of France has some roots to the Friday the 13th superstition, though that is questionable also.

19th century

“In France, Friday 13th might have been associated with misfortune as early as the first half of the 19th century. A character in the 1834 play Les Finesses des Gribouilles states, “I was born on a Friday, December 13th, 1813 from which come all of my misfortunes.” [“Who’s Afraid of Friday the Thirteenth? | Folklife Today”. 12 January 2017.]

“An early documented reference in English occurs in H. S. Edwards‘ biography of Gioachino Rossini, who died on Friday 13th of November 1868:”Rossini was surrounded to the last by admiring friends; and if it be true that, like so many Italians, he regarded Fridays as an unlucky day and thirteen as an unlucky number, it is remarkable that on Friday 13th of November he passed away.” [Edwards, H. S. (1869). The Life of Rossini. Blackett. p. 340.]

Frequency

1. 1.There is always one Friday the 13th in each calendar year.

2. It can be as long as 14 months between two Friday the 13ths, either from July to September of the following year being a common year starting on Tuesday or from August to October the following year being a leap year starting on Saturday.

3. The shortest period that occurs with a Friday the 13th is just one month.

4. There can be no more than three Friday the 13ths in a single calendar year.