Friday the 13th

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Friday the 13th marked on a calendar Freitag der 13. im Kalender.jpg
Friday the 13th marked on a calendar

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, 2015 had a Friday the 13th in February, March, and November, which will happen again in 2026; 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. [1]

Contents

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

History

Unluckiness of "13"

One source mentioned for the unlucky nature of the number "13" is 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. [2] [3]

Christian associations

The Last Supper by Leonardo da Vinci Ultima Cena - Da Vinci 5.jpg
The Last Supper by Leonardo da Vinci

The superstition seems to relate to various things, like 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. [lower-alpha 1] [lower-alpha 2] [6]

In conjunction with Friday

While there is evidence of both Friday [7] and the number 13 [8] being considered unlucky, there is no record of the two items being referred to as especially unlucky in conjunction before the 19th century. [9] [10]

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. [11]

19th century

Gioachino Rossini by Henri Grevedon Rossini by Grevedon.jpg
Gioachino Rossini by Henri Grevedon

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". [12]

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." [13]

Dissemination

It is possible that the publication in 1907 of T. W. Lawson's popular novel Friday, the Thirteenth, [14] 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. [9]

Similar dates

Similar dates are prevalent in many cultures, although it is unclear whether these similarities are in any way historically connected or only coincidental.

Tuesday the 13th in Hispanic and Greek culture

In Spanish-speaking countries, instead of Friday, Tuesday the 13th (martes trece) is considered a day of bad luck. [15]

The Greeks also consider Tuesday (and especially the 13th) an unlucky day. [16] Tuesday is considered dominated by the influence of Ares, the god of war (or Mars, the Roman equivalent). The fall of Constantinople to the Fourth Crusade occurred on Tuesday 13 April 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 (Τρίτη) meaning the third (day of the week), adding weight to the superstition, since bad luck is said to "come in threes". [16]

There is a Tuesday the 13th in months that begin on a Thursday.

Friday the 17th in Italy

An Alitalia airplane without the row 17 Alitalia-17.jpg
An Alitalia airplane without the row 17

In Italian popular culture, Friday the 17th (and not the 13th) is considered a bad luck day. [17] The origin of this belief could be traced in the writing of the number 17, in Roman numerals: XVII. By shuffling the digits of the number one can get the Latin vīxī ("I have lived", implying death at present), an omen of bad luck. [18] In fact, in Italy, 13 is generally considered a lucky number, [19] although some people may consider 13 an unlucky number as well due to Americanization.

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? ("Shriek – Do You Have Something to Do on Friday the 17th?").

There is a Friday the 17th in months starting on Wednesday.

Social impact

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 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 US$ 800–900 million is lost in business on this day. [20] Despite this, representatives for both Delta Air Lines and Continental Airlines (the latter now merged into United Airlines) have stated that their airlines do not suffer from any noticeable drop in travel on those Fridays. [21]

In Finland, a consortium of governmental and nongovernmental organizations led by the Ministry of Social Affairs and Health promotes the National Accident Day (kansallinen tapaturmapäivä) to raise awareness about automotive safety, which always falls on a Friday the 13th. [22] The event is coordinated by the Finnish Red Cross and has been held since 1995. [23]

Rate of accidents

A study by Scanlon, Luben, Scanlon, & Singleton (1993) [24] attracted attention from popular science literature, [lower-alpha 3] [lower-alpha 4] 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"; [24] : 1584  however, the authors clearly state that "the numbers of admissions from accidents are too small to allow meaningful analysis". [24] : 1586  Subsequent studies have disproved any correlation between Friday the 13th and the rate of accidents. [27] [28]

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." [29] [30]

Occurrence

Distribution

Each 400 year Gregorian solar cycle contains 146,097 days (with 97  leap 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. [31] [32] [33]

Distribution of the 13th day per weekday over 4,800 months (400 years)
Day of the weekMondayTuesdayWednesdayThursdayFridaySaturdaySunday
Occurrences685685687684688684687

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 (G, F, GF, etc.) of the year. Years which begin on the same day of the week and are of the same type (i.e. common year or leap year), 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:

Months with the 13th on a Friday for years from 1900 through 2100
Years during which a Friday the 13th
occurs in the month to the right
(current and subsequent year are marked in bold)		Month with
its 13th on
a Friday		Year length
and weekday of
January the 1st		Year's
dominical
letter
20th-century: 1905, 1911, 1922, 1928, 1933, 1939, 1950, 1956, 1961, 1967, 1978, 1984, 1989, 1995;
21st-century: 2006, 2012, 2017, 2023, 2034, 2040, 2045, 2051, 2062, 2068, 2073, 2079, 2090, 2096		January 365: Sunday
366: Sunday 		A
AG
20th-century: 1903, 1914, 1920, 1925, 1931, 1942, 1948, 1953, 1959, 1970, 1976, 1981, 1987, 1998;
21st-century: 2004, 2009, 2015, 2026, 2032, 2037, 2043, 2054, 2060, 2065, 2071, 2082, 2088, 2093, 2099		February 365: Thursday
366: Thursday 		D
DC
20th-century: 1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992; 1998;
21st-century: 2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099		March 365: Thursday
366: Wednesday 		D
ED
20th-century: 1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984; 1990;
21st-century: 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096		April 365: Monday
366: Sunday 		G
AG
20th-century: 1904, 1910, 1921, 1927, 1932, 1938, 1949, 1955, 1960, 1966, 1977, 1983, 1988, 1994;
21st-century: 2005, 2011, 2016, 2022, 2033, 2039, 2044, 2050, 2061, 2067, 2072, 2078, 2089, 2095		May 365: Saturday
366: Friday 		B
CB
20th-century: 1902, 1913, 1919, 1924, 1930, 1941, 1947, 1952, 1958, 1969, 1975, 1980, 1986, 1997;
21st-century: 2003, 2008, 2014, 2025, 2031, 2036, 2042, 2053, 2059, 2064, 2070, 2081, 2087, 2092, 2098		June 365: Wednesday
366: Tuesday 		E
FE
20th-century: 1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984, 1990;
21st-century: 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096		July 365: Monday
366: Sunday 		G
AG
20th-century: 1909, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999;
21st-century: 2004, 2010, 2021, 2027, 2032, 2038, 2049, 2055, 2060, 2066, 2077, 2083, 2088, 2094, 2100		August 365: Friday
366: Thursday 		C
DC
20th-century: 1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;
21st-century: 2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097		September 365: Tuesday
366: Monday 		F
GF
20th-century: 1905, 1911, 1916, 1922, 1933, 1939, 1944, 1950, 1961, 1967, 1972, 1978, 1989, 1995, 2000;
21st-century: 2006, 2017, 2023, 2028, 2034, 2045, 2051, 2056, 2062, 2073, 2079, 2084, 2090		October 365: Sunday
366: Saturday 		A
BA
20th-century: 1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992, 1998;
21st-century: 2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099		November 365: Thursday
366: Wednesday 		D
ED
20th-century: 1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;
21st-century: 2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097		December 365: 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. [34] 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 (F) (e.g. 2001–02, 2012–13 and 2018–19), or from August to October the following year being a leap year starting on Saturday (BA) (e.g. 1999–2000 and 2027–28). 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 (D) (e.g. 2009, 2015 and 2026).

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 (such as 2009, 2015, or 2026) (D), or January, April, and July in a leap year starting on Sunday (such as 1984, 2012, or 2040) (AG). [35]

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. [1] In the 2020s, there were two Friday the 13ths in 2020 and 2023. There will also be three Friday the 13ths in 2026, and two in 2024, and 2029. [1] The remaining years all have at least one Friday the 13th. [1]

For the details see the table below; this table is for the Gregorian calendar and Jan/Feb for leap years:

Year
modulo 28		1600 20001700 21001800 22001900 2300Year
modulo 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   

See also

Footnotes

  1. ↑ There were 13 people at the table (at the Last Supper) and the 13th was Jesus. The Last Supper was on a Thursday, and the next day was Friday, the day of crucifixion. When '13' and Friday come together, it's a double whammy. [4]
  2. ↑ In Christian tradition, fear of Friday the 13th stems from the day of the Crucifixion (Friday) and the number at the [table at the] Last Supper (13 [men]). Despite these origins, the Friday the 13th superstition dates back only to the Middle Ages. [5]
  3. ↑ For starters, a 1993 study published in the British Medical Journal indicates otherwise: Researchers analyzed the traffic flow and number of injuries from car accidents on the southern section of London's M25 motorway during the five months that the 13th fell on a Friday between 1990 and 1992. They compared these numbers to data collected on Friday the 6th of the same months, and found that although there are consistently fewer vehicles on the road during the 13th – possibly as a result of superstitious people choosing not to drive that day, the researchers proposed – "the risk of hospital admission as a result of a transport accident may be increased by as much as 52 percent" on the 13th. [25]
  4. ↑ The study compared hospital admissions for traffic accidents on a Friday the 13th with those on a Friday the 6th in a community outside London. Despite a lower highway traffic volume on the 13th than on the 6th, admissions for traffic accident victims increased 52 percent on the 13th. [26]

Related Research Articles

A leap year is a calendar year that contains an additional day compared to a common year. The 366th day is added to keep the calendar year synchronised with the astronomical year or seasonal year. Since astronomical events and seasons do not repeat in a whole number of days, calendars having a constant number of days each year will unavoidably drift over time with respect to the event that the year is supposed to track, such as seasons. By inserting ("intercalating") an additional day—a leap day—or month—a leap month—into some years, the drift between a civilization's dating system and the physical properties of the Solar System can be corrected.

<span class="mw-page-title-main">Triskaidekaphobia</span> Fear of the number 13

Triskaidekaphobia is fear or avoidance of the number 13. It is also a reason for the fear of Friday the 13th, called paraskevidekatriaphobia or friggatriskaidekaphobia.

13 (thirteen) is the natural number following 12 and preceding 14.

<span class="mw-page-title-main">Friday</span> Day of the week

Friday is the day of the week between Thursday and Saturday. In countries that adopt the traditional "Sunday-first" convention, it is the sixth day of the week. In countries adopting the ISO-defined "Monday-first" convention, it is the fifth day of the week.

A common year starting on Sunday is any non-leap year that begins on Sunday, 1 January, and ends on Sunday, 31 December. Its dominical letter hence is A. The most recent year of such kind was 2023 and the next one will be 2034 in the Gregorian calendar, or, likewise, 2018 and 2029 in the obsolete Julian calendar, see below for more.

A common year starting on Friday is any non-leap year that begins on Friday, 1 January, and ends on Friday, 31 December. Its dominical letter hence is C. The most recent year of such kind was 2021 and the next one will be 2027 in the Gregorian calendar, or, likewise, 2022 and 2033 in the obsolete Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on, and occurs in century years that yield a remainder of 100 when divided by 400. The most recent such year was 1700 and the next one will be 2100.

A common year starting on Monday is any non-leap year that begins on Monday, 1 January, and ends on Monday, 31 December. Its dominical letter hence is G. The most recent year of such kind was 2018 and the next one will be 2029 in the Gregorian calendar, or likewise, 2019 and 2030 in the Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on and occurs in century years that yield a remainder of 300 when divided by 400. The most recent such year was 1900 and the next one will be 2300.

A leap year starting on Sunday is any year with 366 days that begins on Sunday, 1 January, and ends on Monday, 31 December. Its dominical letters hence are AG. The most recent year of such kind was 2012 and the next one will be 2040 in the Gregorian calendar or, likewise 2024 and 2052 in the obsolete Julian calendar.

A common year starting on Tuesday is any non-leap year that begins on Tuesday, 1 January, and ends on Tuesday, 31 December. Its dominical letter hence is F. The most recent year of such kind was 2019 and the next one will be 2030, or, likewise, 2014 and 2025 in the obsolete Julian calendar, see below for more.

A leap year starting on Monday is any year with 366 days that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF. The current year, 2024, is a leap year starting on Monday in the Gregorian calendar. The last such year was 1996 and the next such year will be 2052 in the Gregorian calendar or, likewise, 2008 and 2036 in the obsolete Julian calendar. 29 February falls on Thursday.

A common year starting on Wednesday is any non-leap year that begins on Wednesday, 1 January, and ends on Wednesday, 31 December. Its dominical letter hence is E. The most recent year of such kind was 2014 and the next one will be 2025 in the Gregorian calendar or, likewise, 2015 and 2026 in the obsolete Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on, and occurs in century years that yield a remainder of 200 when divided by 400. The most recent such year was 1800 and the next one will be 2200.

A leap year starting on Tuesday is any year with 366 days that begins on Tuesday, 1 January, and ends on Wednesday, 31 December. Its dominical letters hence are FE. The most recent year of such kind was 2008 and the next one will be 2036 in the Gregorian calendar or, likewise 2020 and 2048 in the obsolete Julian calendar.

A common year starting on Saturday is any non-leap year that begins on Saturday, 1 January, and ends on Saturday, 31 December. Its dominical letter hence is B. The most recent year of such kind was 2022 and the next one will be 2033 in the Gregorian calendar or, likewise, 2023 and 2034 in the obsolete Julian calendar. See below for more.

A common year starting on Thursday is any non-leap year that begins on Thursday, 1 January, and ends on Thursday, 31 December. Its dominical letter hence is D. The most recent year of such kind was 2015 and the next one will be 2026 in the Gregorian calendar or, likewise, 2021 and 2027 in the obsolete Julian calendar, see below for more.

A leap year starting on Saturday is any year with 366 days that begins on Saturday, 1 January, and ends on Sunday, 31 December. Its dominical letters hence are BA. The most recent year of such kind was 2000 and the next one will be 2028 in the Gregorian calendar or, likewise 2012 and 2040 in the obsolescent Julian calendar. In the Gregorian calendar, years divisible by 400 are always leap years starting on Saturday. The most recent such occurrence was 2000 and the next one will be 2400, see below for more.

A leap year starting on Friday is any year with 366 days that begins on Friday 1 January and ends on Saturday 31 December. Its dominical letters hence are CB. The most recent year of such kind was 2016 and the next one will be 2044 in the Gregorian calendar or, likewise, 2000 and 2028 in the obsolete Julian calendar.

A leap year starting on Thursday is any year with 366 days that begins on Thursday 1 January, and ends on Friday 31 December. Its dominical letters hence are DC. The most recent year of such kind was 2004 and the next one will be 2032 in the Gregorian calendar or, likewise, 2016 and 2044 in the obsolete Julian calendar.

A leap year starting on Wednesday is any year with 366 days that begins on Wednesday 1 January and ends on Thursday 31 December. Its dominical letters hence are ED. The most recent year of such kind was 2020 and the next one will be 2048 in the Gregorian calendar, or likewise, 2004 and 2032 in the obsolete Julian calendar, see below for more.

<span class="mw-page-title-main">Heptadecaphobia</span> Fear of the number 17

Heptadecaphobia or heptadekaphobia is the fear of the number 17. It is considered to be ill-fated in Italy and other countries of Greek and Latin origins, while the date Friday the 17th is considered especially unfortunate in Italy. The number is feared due to superstition, and is similar in nature to the fear of the number 13 in Anglo-Saxon countries.

References

  1. 1 2 3 4 "Months and years having Friday the 13th". Time and Date (timeanddate.com).
  2. ↑ "Friday the 13th Superstitions Rooted in Bible and More". National Geographic . Archived from the original on 9 October 2019.
  3. ↑ "Why is Friday the 13th Considered Unlucky?". Mental Floss . 13 July 2018.
  4. ↑ Della Contrada, John (9 February 2004). "Fear of "Friday the 13th may likely have originated from Jesus' last supper and crucifixion", says U.B. anthropologist". Buffalo, NY: U. Buffalo / SUNY . Retrieved 13 July 2014.
  5. ↑ Hartston, Willam (2007). Encyclopedia of Useless Information. Sourcebooks, Inc. p. 365. ISBN   978-1402248382.
  6. ↑ Vyse, Stuart (13 October 2017). "Why we fear Friday the 13th". CNN. Archived from the original on 14 April 2021. Retrieved 28 May 2022.
  7. ↑ Friday has been considered an unlucky day to undertake journeys or begin new projects at least since the 14th century, as witnessed by Chaucer's Canterbury Tales Opie, Iona; Tatem, Moira (2003). "FRIDAY an unlucky day". A Dictionary of Superstitions. Oxford Reference. ISBN   9780192829160.
  8. ↑ Opie, Iona; Tatem, Moira (2003). "THIRTEEN unlucky number". A Dictionary of Superstitions. Oxford Reference. ISBN   9780192829160.
  9. 1 2 Lachenmeyer, Nathaniel (2004). "5". 13: The Story of the World's Most Popular Superstition. Penguin Group (USA) Incorporated. ISBN   9780452284968.
  10. ↑ Clar, Mimi (1957). "Friday the 13th". Western Folklore. 16 (1): 62–63. doi:10.2307/1497075. JSTOR   1497075.
  11. ↑ "Friday the 13th - Origins, History & Superstition". HISTORY. 10 August 2021. Retrieved 25 November 2023.
  12. ↑ "Who's Afraid of Friday the Thirteenth? | Folklife Today". 12 January 2017.
  13. ↑ Edwards, H. S. (1869). The Life of Rossini. Blackett. p. 340.
  14. ↑ Lawson, T. W. (1907). Friday, the Thirteenth (original magazine serialization ed.). Retrieved 13 May 2011– via Gutenberg.org.{{cite book}}: |magazine= ignored (help)
  15. ↑ Falcón, Rafael; Falcón, Christine Yoder (1998). Salsa: A taste of Hispanic culture. Praeger. p. 64. ISBN   0-275-96121-4 – via Google Books.
  16. 1 2 Chrysopoulos, Philip (13 October 2015). "Why superstitious Greeks fear Tuesday the 13th". Greek Reporter. Retrieved 31 October 2016.
  17. ↑ Grande, Carlo (17 February 2012). "Venerdì 17 porta davvero sfortuna?". La Stampa (in Italian). Archived from the original on 18 August 2012. Retrieved 31 March 2012.
  18. ↑ Nick Harris (15 November 2007). "Bad omen for Italy as their unlucky number comes up". The Independent . Retrieved 15 February 2015.
  19. ↑ "Venerdì 13 porta (s)fortuna? Non in Italia". cafebabel.com (in Italian). Archived from the original on 8 June 2013. Retrieved 31 March 2012.
  20. ↑ Roach, John (12 August 2004). "Friday the 13th phobia rooted in ancient history". National Geographic News. Archived from the original on 3 June 2004. Retrieved 29 October 2008.
  21. ↑ Sens, Josh (January–February 2004). "Friday the 13th: Lucky or unlucky". Via Magazine. American Automobile Association. Archived from the original on 16 August 2010. Retrieved 13 August 2021. When the 13th of the month falls on a Friday, do you join the 21 million Americans who suffer paraskevidekatriaphobia?
  22. ↑ "Tapaturmapäivä 13.9.2013: erityisteemana työpaikkojen turvallisuustyö" [Accident day 13 Sep 2013: Special workplace safety work]. tyosuojelu.fi (in Finnish). 27 June 2013. Archived from the original on 29 April 2014. Retrieved 28 April 2014.
  23. ↑ "Mikä on Tapaturmapäivä?". www.kotitapaturma.fi (in Finnish). 30 March 2016. Retrieved 9 January 2018.
  24. 1 2 3 Scanlon, T.J.; Luben, R.N.; Scanlon, F.L.; Singleton, N. (18 December 1993). "Is Friday the 13th bad for your health?". British Medical Journal . 307 (6919): 1584–1586. doi:10.1136/bmj.307.6919.1584. ISSN   0959-8138. PMC   1697765 . PMID   8292946.
  25. ↑ Melina, Remy (13 January 2012). "Statistically speaking, is Friday the 13th really unlucky?". Live Science . Retrieved 13 April 2018.
  26. ↑ Gawande, A. (20 March 1998). "When a full moon and a lunar eclipse collide with Friday the 13th, do more accidents really happen?". Slate . Retrieved 13 April 2018.
  27. ↑ Lo, Bruce M.; Visintainer, Catherine M.; Best, Heidi A.; Beydoun, Hind A. (July 2012). "Answering the myth: Use of emergency services on Friday the 13th". The American Journal of Emergency Medicine . 30 (6): 886–889. doi:10.1016/j.ajem.2011.06.008. PMID   21855260.
  28. ↑ Schuld, Jochen; Slotta, Jan E.; Schuld, Simone; Kollmar, Otto; Schilling, Martin K.; Richter, Sven (1 September 2011). "Popular belief meets surgical reality: Impact of Lunar phases, Friday the 13th, and Zodiac signs on emergency operations and intraoperative blood loss". World Journal of Surgery . 35 (9): 1945–1949. doi:10.1007/s00268-011-1166-8. ISSN   0364-2313. PMID   21713579. S2CID   23787395.
  29. ↑ "Friday 13th is no longer unlucky". Mirror (mirror.co.uk). Daily Mirror. 4 February 2012 [13 Jun 2008].
  30. ↑ "Friday 13th not more unlucky, Dutch study shows". Reuters . 13 June 2008.
  31. ↑ Bodin, Magnus (13 November 1998). "About the date+day distribution along the epoch". x42. Retrieved 30 January 2014.
  32. ↑ Brown, B.H. & Robinson, Raphael (1933). "Solution to problem E36". American Mathematical Monthly . 40 (10): 607. doi:10.2307/2301694. JSTOR   2301694.
  33. ↑ Meeus, J. (2007). Mathematical Astronomy Morsels IV. p. 367.
  34. ↑ Golomb, Solomon (September 2007). "Solutions to 'Calendar oddities'". Golomb's Gambits. Johns Hopkins Magazine. Vol. 59, no. 4.
  35. ↑ Kher, Aparna. "13 Facts about Friday the 13th". Time and Date (timeanddate.com).
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