Friday the 13th


Friday the 13th is considered an unlucky day in Western superstition. It occurs when the 13th day of the month in the Gregorian calendar falls on a Friday, which happens at least once every year but can occur up to three times in the same year.
For a month to have a Friday the 13th, the first day of the month must be a Sunday.

Origins

Unluckiness of 13

One source mentioned for the unlucky reputation of the number 13 is a Norse myth about twelve gods having a dinner party in Valhalla. 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.

Christian associations

The superstition seems to relate to various things, like the story of Jesus's Last Supper and crucifixion in which there were thirteen individuals present in the Upper Room on the thirteenth of Nisan Maundy Thursday, the night before his death on Good Friday.

In conjunction with 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

Some cite the arrest of the Knights Templar on Friday, October 13, 1307, by officers of King Philip IV of France as the origin of the Friday the 13th superstition, but it is agreed the origins remain murky.

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".
An early documented reference in English occurs in H. S. Edwards' biography of Gioachino Rossini, who died on Friday 13th of November 1868:

Dissemination

It is possible that the publication in 1907 of T. W. Lawson's popular novel Friday, the Thirteenth,
contributed to popularizing the superstition. In the novel, an unscrupulous broker takes advantage of the superstition to create a Wall Street panic on a Friday the 13th.

Occurrence

Distribution

Each 400-year Gregorian solar cycle contains 146,097 days or exactly 20,871 weeks. Each cycle contains the same pattern of days of the week and therefore the same pattern of Fridays that are on the 13th. The 13th day of the month is very slightly more likely to be a Friday than any other day of the week.
Any month that starts on a Sunday contains a Friday the 13th, and there is at least one Friday the 13th in every calendar year.
The months with a Friday the 13th are determined by the Dominical letter of the year. Years which begin on the same day of the week and are of the same type, will have a Friday the 13th in the same months.
This sequence, given here for 1900–2099, follows a 28-year cycle from 1 March 1900 to 28 February 2100:
Years during which a Friday the 13th
occurs in the month to the right
Month with
its 13th on
a Friday		Year length
and weekday of
January the 1st		Year's
dominical
letter
1905, 1911, 1922, 1928, 1933, 1939, 1950, 1956, 1961, 1967, 1978, 1984, 1989, 1995;
2006, 2012, 2017, 2023, 2034, 2040, 2045, 2051, 2062, 2068, 2073, 2079, 2090, 2096		January365: Sunday
366: Sunday		A
AG
1903, 1914, 1920, 1925, 1931, 1942, 1948, 1953, 1959, 1970, 1976, 1981, 1987, 1998;
2004, 2009, 2015, 2026, 2032, 2037, 2043, 2054, 2060, 2065, 2071, 2082, 2088, 2093, 2099		February365: Thursday
366: Thursday		D
DC
1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992; 1998;
2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099		March365: Thursday
366: Wednesday		D
ED
1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984; 1990;
2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096		April365: Monday
366: Sunday		G
AG
1904, 1910, 1921, 1927, 1932, 1938, 1949, 1955, 1960, 1966, 1977, 1983, 1988, 1994;
2005, 2011, 2016, 2022, 2033, 2039, 2044, 2050, 2061, 2067, 2072, 2078, 2089, 2095		May365: Saturday
366: Friday		B
CB
1902, 1913, 1919, 1924, 1930, 1941, 1947, 1952, 1958, 1969, 1975, 1980, 1986, 1997;
2003, 2008, 2014, 2025, 2031, 2036, 2042, 2053, 2059, 2064, 2070, 2081, 2087, 2092, 2098		June365: Wednesday
366: Tuesday		E
FE
1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984, 1990;
2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096		July365: Monday
366: Sunday		G
AG
1909, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999;
2004, 2010, 2021, 2027, 2032, 2038, 2049, 2055, 2060, 2066, 2077, 2083, 2088, 2094, 2100		August365: Friday
366: Thursday		C
DC
1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;
2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097		September365: Tuesday
366: Monday		F
GF
1905, 1911, 1916, 1922, 1933, 1939, 1944, 1950, 1961, 1967, 1972, 1978, 1989, 1995, 2000;
2006, 2017, 2023, 2028, 2034, 2045, 2051, 2056, 2062, 2073, 2079, 2084, 2090		October365: Sunday
366: Saturday		A
BA
1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992, 1998;
2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099		November365: Thursday
366: Wednesday		D
ED
1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;
2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097		December365: Tuesday
366: Monday		F
GF

Frequency

Although there is always at least one Friday the 13th per calendar year, it can be as long as 14 months between two Friday the 13ths. The longest period that occurs without a Friday the 13th is 14 months, either from July to September 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 . The shortest period that occurs with a Friday the 13th is just one month, from February to March in a common year starting on Thursday .
On average, there is a Friday the 13th once every 212.35 days. Friday the 13ths occurs with an average frequency of 1.7218 per year or about 3477 since the year 1 CE.

Frequency within a single year

There can be no more than three Friday the 13ths in a single calendar year; either in February, March, and November in a common year starting on Thursday , or January, April, and July in a leap year starting on Sunday .
In the 2000s, there were three Friday the 13ths in 2009, and two Friday the 13ths in 2001, 2002, 2006, and 2007. In the 2010s, there were three Friday the 13ths in 2012 and 2015, and two in 2013, 2017, 2018, and 2019. In the 2020s, there were two Friday the 13ths in 2020, 2023 and 2024. There will also be three Friday the 13ths in 2026, and two in 2029. The remaining years all have one Friday the 13th.
For the details see the table below; this table is for the Gregorian calendar and / for :

Social influence

According to the Stress Management Center and Phobia Institute in Asheville, North Carolina, an estimated 17–21 million people in the United States are affected by Paraskevidekatriaphobia, making it the most feared day and date in history. Some people are so paralyzed by fear that they avoid their normal routines in doing business, taking flights or even getting out of bed. It has been estimated that US$ 800–900 million is lost in business on this day.
Despite this, representatives for both Delta Air Lines and Continental Airlines have stated that their airlines do not suffer from any noticeable drop in travel on those Fridays.
In Finland, a consortium of governmental and nongovernmental organizations led by the Ministry of Social Affairs and Health promotes the National Accident Day to raise awareness about automotive safety, which always falls on a Friday the 13th.
The event is coordinated by the Finnish Red Cross and has been held since 1995.

Rate of accidents

A study by Scanlon, Luben, Scanlon, & Singleton
attracted attention from popular science literature,
as it concluded that "the risk of hospital admission as a result of a transport accident may be increased by as much as 52 percent on the 13th";
however, the authors clearly state that "the numbers of admissions from accidents are too small to allow meaningful analysis".
Subsequent studies have disproved any correlation between Friday the 13th and the rate of accidents.
On 12 June 2008 the Dutch Centre for Insurance Statistics stated to the contrary, that "fewer accidents and reports of fire and theft occur when the 13th of the month falls on a Friday than on other Fridays, because people are preventatively more careful or just stay home. Statistically speaking, driving is slightly safer on Friday the 13th, at least in the Netherlands; in the last two years, Dutch insurers received reports of an average 7,800 traffic accidents each Friday; but the average figure when the 13th fell on a Friday was just 7,500."