Friday the 13th
According to folklorists, there is no written evidence for a "Friday the 13th" superstition before the 19th century. The earliest known documented reference in English occurs in Henry Sutherland Edwards' 1869 biography of Gioachino Rossini, who died on a Friday 13th.
He [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.
- In numerology, the number twelve is considered the number of divine organizational arrangement or chronological completeness, as reflected in the twelve months of the year, twelve hours of the clock day, the twelve deities of Olympus, twelve tribes of Israel, twelve Apostles of Jesus, the 12 successors of Muhammad in Shia Islam, twelve signs of the Zodiac, the 12 years of the Buddhist cycle, etc., whereas the number thirteen was considered irregular, transgressing this completeness. There is also a superstition, thought by some to derive from the Last Supper or a Norse myth, that having thirteen people seated at a table results in the death of one of the diners.
- Friday has been considered an unlucky day at least since the 14th century's The Canterbury Tales, and many other professions have regarded Friday as an unlucky day to undertake journeys or begin new projects.
- Christians commemorate the crucifixion of Jesus on the Friday before Easter.
- One author, noting that references are all but nonexistent before 1907 but frequently seen thereafter, has argued that its popularity derives from the publication that year of Thomas W. Lawson's popular novel Friday, the Thirteenth, in which an unscrupulous broker takes advantage of the superstition to create a Wall Street panic on a Friday the 13th.
- Records of the superstition are rarely found before the 20th century, when it became extremely common. The connection between the Friday the 13th superstition and the Knights Templar was popularized in Dan Brown's 2003 novel The Da Vinci Code and in John J. Robinson's 1989 work Born in Blood: The Lost Secrets of Freemasonry, and also in the Maurice Druon historical novel series: "The Accursed Kings" (French: Les Rois Maudits). On Friday, 13 October 1307, hundreds of the Knights Templar were arrested in France, an action apparently motivated financially and undertaken by the efficient royal bureaucracy to increase the prestige of the crown. Philip IV was the force behind this ruthless move, but it has also tarnished the historical reputation of Clement V. From the very day of Clement V's coronation, the king falsely charged the Templars with heresy, immorality and abuses, and the scruples of the Pope were compromised by a growing sense that the burgeoning French State might not wait for the Church, but would proceed independently. It is further said Jacques de Molay, Magister (Master of the Knights of the Temple) cursed King Philip IV of France and his descendants from his execution pyre. As he was about to be executed, he appealed “from this your heinous judgement to the living and true God, who is in Heaven”, warning the pope that, within a year and a day, he and Philip IV would be obliged to answer for their crimes in God’s presence. Philip and Clement V both died within a year of Molay’s execution. However, experts agree that this is a relatively recent correlation, and most likely a modern-day invention.
Phobia names and etymology
The fear of Friday the 13th has been called friggatriskaidekaphobia (Frigga being the name of the Norse goddess for whom "Friday" is named in English and triskaidekaphobia meaning fear of the number thirteen), or paraskevidekatriaphobia a concatenation of the Greek words Paraskeví (Παρασκευή, meaning "Friday"), and dekatreís (δεκατρείς, meaning "thirteen") attached to phobía (φοβία, from phóbos, φόβος, meaning "fear"). The latter word was derived in 1911 and first appeared in a mainstream source in 1953. 
On the other hand, Friday is a religious day for Muslims where they perform Friday 'Jumaa' Prayer in congregation. The number 13th being an odd number is also blessed in Islam, as the prophet Muhammad liked odd numbers.
Tuesday the 13th (Hispanic & Greek culture)
In Spanish-speaking countries, instead of Friday, Tuesday the 13th (martes trece) is considered a day of bad luck. The Greeks also consider Tuesday (and especially the 13th) an unlucky day. Tuesday is considered dominated by the influence of Ares, the god of war. A connection can be seen in the etymology of the name in some European languages (Mardi in French or martes in Spanish). 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, May 29, 1453, events that strengthen the superstition about Tuesday. In addition, in Greek the name of the day is Triti (Τρίτη) meaning literally the third (day of the week), adding weight to the superstition, since bad luck is said to "come in threes".[dubious ]
Friday the 17th (Italy)
In Italian popular culture, Friday the 17th (and not the 13th) is considered a day 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? ("Shriek – Do You Have Something to Do on Friday the 17th?").
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 [US]$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, which always falls on a Friday 13th.
Rate of accidents
A study in the British Medical Journal, published in 1993, concluded that there "is a significant level of traffic-related incidences on Friday the 13th as opposed to a random day, such as Friday the 6th, in the UK." However, the Dutch Centre for Insurance Statistics (CVS) 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."
The following months have a Friday the 13th:
|January||1978, 1984, 1989, 1995, 2006, 2012, 2017, 2023||A, AG|
|February||1976, 1981, 1987, 1998, 2004, 2009, 2015, 2026||D, DC|
|March||1981, 1987, 1992, 1998, 2009, 2015, 2020, 2026||D, ED|
|April||1979, 1984, 1990, 2001, 2007, 2012, 2018, 2029||G, AG|
|May||1977, 1983, 1988, 1994, 2005, 2011, 2016, 2022||B, CB|
|June||1975, 1980, 1986, 1997, 2003, 2008, 2014, 2025||E, FE|
|July||1979, 1984, 1990, 2001, 2007, 2012, 2018, 2029||G, AG|
|August||1976, 1982, 1993, 1999, 2004, 2010, 2021, 2027||C, DC|
|September||1974, 1985, 1991, 1996, 2002, 2013, 2019, 2024||F, GF|
|October||1978, 1989, 1995, 2000, 2006, 2017, 2023, 2028||A, BA|
|November||1981, 1987, 1992, 1998, 2009, 2015, 2020, 2026||D, ED|
|December||1974, 1985, 1991, 1996, 2002, 2013, 2019, 2024||F, GF|
This sequence given here for 2001–2028, 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 (G, F, GF, etc.) 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 (D) (such as 2009 or 2015), or January, April and July in a leap year starting on Sunday (AG) (such as 2012).
The longest period that can occur without a Friday the 13th is fourteen months, either from July to September the following common year (e.g., between 2001–02, 2012–13, and 2018–19), or from August to October the following leap year (e.g., between 1999–2000 or 2027–28).
Patterns for common years:
Each Gregorian 400-year cycle contains 146,097 days (365 × 400 = 146,000 normal days, plus 97 leap days). 146,097 days ÷ 7 days per week = 20,871 weeks. Thus, 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 (compared to Thursday the 13th, which occurs only once every 213.59 days).
The distribution of the 13th day over the 4,800 months is as follows:
|Day of the week||Sunday||Monday||Tuesday||Wednesday||Thursday||Friday||Saturday|
|Number of occurrences||687||685||685||687||684||688||684|
The above shows that the most encountered combination (day of month, day of week) with day of month = 13th is the one with day of week = Friday. One could consider also the question about the most encountered combinations (day of month, day of week) with day of week = Friday. These turn out to be the ones with day of month equal to 6th, 13th, 20th or 27th. This can be seen as follows:
Since the 6th, the 13th, the 20th and 27th day of a month fall on one and the same day of the week, they have one and the same distribution over the months. Hence the 6th, the 20th and 27th day of a month happen to be Fridays as often as the 13th one does, i.e. each of these days also falls on a Friday exactly 688 times during the 400-year Gregorian cycle. All other days of the month have a smaller frequency of falling on a Friday. For instance, the 7th of a month falls on a Friday if and only if the 13th of this month falls on a Thursday, therefore, according to the above table, the 7th falls on a Friday exactly 684 times during the same time period. A small modification of this reasoning is needed for the 29th, the 30th and the 31st days of a month, because there are months without some or all of these days in them. The reasoning for the 29th day of the month looks as follows. Whenever there is such a day in a month (i.e. the month is not February or the year is a leap year) and the day is a Friday, then the 13th of this month is a Wednesday. Therefore, again according to the table above, there are at most 687 cases of Friday the 29th during the 400-year Gregorian cycle (actually there are less than 687 such cases, since the 13th of a month can be a Wednesday without the presence of a 29th day in the month – such is, for instance, the case with February 2013). The reasoning for the 30th of the month is similar. In any month with Friday the 30th, the 13th of the month is a Tuesday, hence there are at most 685 such months in the 400-year cycle (their count is actually smaller, since, for instance, the 13th of February 2007 is a Tuesday, and there is no 30th day in February). Finally, in any month with Friday the 31st, the 13th of the month is a Monday, hence there are at most 685 such months in the 400-year cycle (since, for instance, the 13th of February 2012 is a Monday, the count of these months is actually smaller).
- Nathaniel Lachenmeyer, 13: The Story of the World's Most Popular Superstition ch. 5 (2004).
- Roach, John (12 August 2004). "Friday the 13th Phobia Rooted in Ancient History". National Geographic News. Retrieved 29 October 2008.
- Clar, Mimi (1957). "Friday the 13th". Western Folklore: 62–63.
- Henry Sutherland Edwards, The Life of Rossini, Blackett, 1869, p.340.
- Weisstein, Eric W. "Triskaidekaphobia on MathWorld". MathWorld. Retrieved 14 August 2010.
- Thomas W. Lawson. "Thomas W. Lawson, ''Friday, the Thirteenth'' (1907)". Gutenberg.org. Retrieved 13 May 2011.
- Howarth, Stephen (1992). The Knights Templar. Barnes and Noble. ISBN 978-0-88029-663-2.
- "Friday the 13th". snopes.com. Retrieved 26 March 2007.
- "Why Friday the 13th Is Unlucky". Urbanlegends.about.com. Retrieved 13 May 2011.
- Alternative spellings include paraskevodekatriaphobia.
- "Snopes.com". Snopes.com. Retrieved 13 May 2011.
- name=mathworld>Weisstein, Eric W. "Triskaidekaphobia on MathWorld". MathWorld. Retrieved 14 August 2010.
- Rafael Falcón, Christine Yoder Falcón Salsa: a taste of Hispanic culture, p. 64, Praeger (1998), ISBN 0-275-96121-4
- (Italian) Carlo Grande (17 February 2012). "Venerdì 17 porta davvero sfortuna?". La Stampa. Retrieved 31 March 2012.
- (Italian) "Venerdì 13 porta (s)fortuna? Non in Italia". cafebabel.com. Retrieved 31 March 2012.
- (Italian) "Venerdì 13 è un giorno che porta sfortuna – Mara rimanda le nozze con Mezzaroma". Corriere del Mezzogiorno. 1 February 2011. Retrieved 31 March 2012.
- Josh Sens, "Some Don't Count on lucky", Via Magazine, January 2004.
- http://www.tyosuojelu.fi/fi/ajankohtaista/5757 http://www.tapaturmapäivä.fi/fi/
- Roach, John. "Friday the 13th Phobia Rooted in Ancient History". National Geographic Society (in English). Retrieved 15 June 2014. "According to a 1993 study in the British Medical Journal, however, there is a significant level of traffic-related incidences on Friday the 13th as opposed to a random day, such as Friday the 6th, in the UK."
- Mirror.co.uk, "Friday 13th is no longer unlucky".
- Dutch study shows Friday 13th not more unlucky, Reuters.com
- Bodin, Magnus (13 November 1998). "About the date+day-distribution along the epoch". x42. Retrieved 13 November 1998.
- B.H. Brown and Raphael Robinson, "Solution to Problem E36", American Mathematical Monthly, vol. 40, issue 10 (1933), p. 607; Jean Meeus, Mathematical Astronomy Morsels IV, 2007, p. 367.
|Look up paraskavedekatriaphobia in Wiktionary, the free dictionary.|
- Some don't count on Lucky 13 – Via Magazine
- Calendar Showing Friday 13s, Robslink.com
- S&P 500 Performance on Friday 13s, dailyspeculations.com
- All Ords Performance on Friday 13s, asxiq.com