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 example, in 2015, Friday the 13th occurred in February, March, and November. 2017 through 2020 will all have two Friday the 13ths each, and the years 2021 and 2022 will both have just one occurrence each.
Friday the 13th occurs in any month that begins on a Sunday.

History

The irrational fear of the number 13 has been given a scientific name: "triskaidekaphobia"; and on analogy to this the fear of Friday the 13th is called paraskevidekatriaphobia, from the Greek words Paraskeví, and dekatreís.
According to folklore historian Donald Dossey, the unlucky nature of the number "13" originated with a Norse myth about 12 gods having a dinner party in Valhalla. The trickster god Loki, who was not invited, arrived as the 13th guest, and arranged for Höðr to shoot Balder with a mistletoe-tipped arrow. Dossey: "Balder died, and the whole Earth got dark. The whole Earth mourned. It was a bad, unlucky day." This major event in Norse mythology caused the number 13 to be considered unlucky.
The superstition may have also arisen in the Middle Ages, "originating from the story of Jesus' last supper and crucifixion" in which there were 13 individuals present in the Upper Room on the 13th of Nisan Maundy Thursday, the night before his death on Good 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.
An early documented reference in English occurs in Henry Sutherland Edwards' 1869 biography of Gioachino Rossini, who died on a Friday 13th:
He 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.

It is possible that the publication in 1907 of Thomas W. Lawson's popular novel Friday, the Thirteenth, contributed to disseminating the superstition. In the novel, an unscrupulous broker takes advantage of the superstition to create a Wall Street panic on a Friday the 13th.
A suggested origin of the superstition—Friday, 13 October 1307, the date Philip IV of France arrested hundreds of the Knights Templar—may not have been formulated until the 20th century. It is mentioned in the 1955 Maurice Druon historical novel The Iron King, John J. Robinson's 1989 work Born in Blood: The Lost Secrets of Freemasonry, Dan Brown's 2003 novel The Da Vinci Code and Steve Berry's The Templar Legacy.

Tuesday the 13th in Hispanic and Greek culture

In Spanish-speaking countries, instead of Friday, Tuesday the 13th is considered a day of bad luck.
The Greeks also consider Tuesday an unlucky day. Tuesday is considered dominated by the influence of Ares, the god of war. The fall of Constantinople to the Fourth Crusade occurred on Tuesday, April 13, 1204, and the Fall of Constantinople to the Ottomans happened on Tuesday, 29 May 1453, events that strengthen the superstition about Tuesday. In addition, in Greek the name of the day is Triti meaning the third, adding weight to the superstition, since bad luck is said to "come in threes".
Tuesday the 13th occurs in a month that begins on a Thursday.

Friday the 17th in Italy

In Italian popular culture, Friday the 17th is considered a day of bad luck. The origin of this belief could be traced in the writing of number 17, in Roman numerals:. By shuffling the digits of the number one can easily get the word , an omen of bad luck. In fact, in Italy, 13 is generally considered a lucky number. However, due to Americanization, young people consider Friday the 13th unlucky as well.
The 2000 parody film Shriek If You Know What I Did Last Friday the Thirteenth was released in Italy with the title Shriek – Hai impegni per venerdì 17?.
Friday the 17th occurs on a month starting on Wednesday.

Social impact

According to the Stress Management Center and Phobia Institute in Asheville, North Carolina, an estimated 17 to 21 million people in the United States are affected by a fear of this day, 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's been estimated that United States dollar|$800 or $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 in the British Medical Journal, published in 1993, attracted some 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 the contrary, the Dutch Centre for Insurance Statistics on 12 June 2008 stated 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."

Occurrence

In years which begin on the same day of the week and are of the same type, Friday the 13th occurs in the same months.
MonthYearsYear categoryDominical letter
January1905, 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, 2096Common: Sunday, Leap: SundayA, AG
February1903, 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, 2099Common: Thursday, Leap: ThursdayD, DC
March1903, 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, 2099Common: Thursday, Leap: WednesdayD, ED
April1900, 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, 2096Common: Monday, Leap: SundayG, AG
May1904, 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, 2095Common: Saturday, Leap: FridayB, CB
June1902, 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, 2098Common: Wednesday, Leap: TuesdayE, FE
July1900, 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, 2096Common: Monday, Leap: SundayG, AG
August1909, 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, 2100Common: Friday, Leap: ThursdayC, DC
September1901, 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, 2097Common: Tuesday, Leap: MondayF, GF
October1905, 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, 2090Common: Sunday, Leap: SaturdayA, BA
November1903, 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, 2099Common: Thursday, Leap: WednesdayD, ED
December1901, 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, 2097Common: Tuesday, Leap: MondayF, GF

This sequence, given here for 1900–2099, follows a 28-year cycle from 1 March 1900 to 28 February 2100. The months with a Friday the 13th are determined by the Dominical letter of the year. 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. There can be as many as 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 .
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 .
Each Gregorian 400-year cycle contains 146,097 days or exactly 20,871 weeks. Therefore, each cycle contains the same pattern of days of the week and thus the same pattern of Fridays that are on the 13th. The 13th day of the month is slightly more likely to be a Friday than any other day of the week. On average, there is a Friday the 13th once every 212.35 days, whereas Thursday the 13th occurs only once every 213.59 days.
Day of the weekMondayTuesdayWednesdayThursdayFridaySaturdaySunday
Occurrences685685687684688684687

Frequency

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 will be three F13s in 2026, and two in 2020, 2023, 2024, and 2029. The rest of years have at least one F13 if there are fewer than two or three in the 2010s and 2020s. Assuming nothing is changed with the calendar, there are never more than three F13s in a year. There is a 28-year cycle that repeats when there is a F13 in February, March and November, and the current start of that pattern was in 2009. Although there is at least one F13 per calendar year, it can be as long as 14 months between two F13s. For the details see the table below.
Year mod 281600 20001700 21001800 22001900 2300Year mod 28
00 06   17 23Jan OctFeb AugJunJan Apr Jul00 06   17 23
01 07 12 18  Jan Apr JulMayFeb Mar NovSep Dec01 07 12 18  
02   13 19 24Sep DecJan OctFeb AugJun02   13 19 24
03 08 14   25JunJan Apr JulMayFeb Mar Nov03 08 14   25
  09 15 20 26Feb Mar NovSep DecJan OctFeb Aug  09 15 20 26
04 10   21 27Feb AugJunJan Apr JulMay04 10   21 27
05 11 16 22  MayFeb Mar NovSep DecJan Oct05 11 16 22  

The table is for the Gregorian calendar and Jan/Feb for leap years.