paraskevodekatriaphobia or paraskevidekatriaphobia or friggatriskaidekaphobia, and is a specialized form of triskaidekaphobia, a phobia (fear) of the number thirteen.
Before the 19th century, though the number 13 was considered unlucky, and Friday was considered unlucky, there was no link between them. The first documented mention of a "Friday the 13th" is generally listed as occurring in the early 1900s.
However, documentation aside, many popular stories exist about the origin of the concept:
The Last Supper, with stories that Judas was the thirteenth guest, and that the Crucifixion of Jesus occurred Friday.
That the biblical Eve offered the fruit to Adam on a Friday, and that the slaying of Abel happened on a Friday (though the Bible does not identify the days of the week when these events occurred).
That it started on Friday, October 13, 1307, the date that many Knights Templar were simultaneously arrested in France, by agents of King Philip IV.
However, historically, there is no true date that the Friday the 13th superstition can be linked to.
In the case of Greece, Tuesday, April 13, 1204 was the date that Constantinople was sacked by the crusaders of the fourth crusade. The first ever fall of the then richest Christian city, and the looting that followed, allegedly gave Tuesday 13 its bad meaning. Ironically enough, Constantinople fell for the second time in its history on Tuesday, May 29, 1453, to the Ottoman Turks, a date that puts an end to the Byzantine empire, and to Greek sovereignty for several centuries, and therefore reinforcing Tuesday as an unlucky day in the Greek world.
Many modern stories (including The Da Vinci Code) claim that when King Philip IV had many Templars simultaneously arrested on October 13, 1307, that started the legend of the unlucky Friday the 13th. However, closer examination shows that though the number 13 was indeed considered historically unlucky, the actual association of Friday and 13 seems to be an invention from the early 1900s.
"It's been estimated that [U.S] $800 or $900 million is lost in business on this day because people will not fly or do business they would normally do."
Some people are so paralyzed by fear that they are simply unable to get out of bed when Friday the 13th rolls around. The Stress Management Center and Phobia Institute estimates that more than 17 million people are affected by a fear of this day. Despite that, representatives for both Delta and Continental Airlines say that their airlines don't suffer from any noticeable drop in travel on those Fridays.
A British Medical Journal study has shown that there is a significant increase in traffic related accidents on Friday the 13ths.
The date is well-known in the motorcycle (biker) community: Since 1981, motorcycle enthusiasts and vendors gather every Friday the 13th in Port Dover, Ontario, Canada. This tradition started on November 13, 1981 by Chris Simons as a gathering of approximately 25 friends. The event has grown substantially, with an estimated 100,000 people attending in August 2004, as well as music bands, vendors, a bike show, etc.
In the Spanish-speaking world, it is Tuesday the 13th the day that supposedly brings bad luck; a proverb runs En martes, ni te cases ni te embarques, ni de tu familia te apartes. (On Tuesday, neither get married nor start a journey, or separate yourself from your family.)
All months whose first day falls on a Sunday will contain a Friday the 13th.
Every year has at least one and at most three Fridays the 13th, with 48 occurences in 28 years an average of 1.7 times per year.
The Gregorian Calendar 400-year cycle contains a whole number (20,871) of weeks and 146,097 days, but the number of months (4800) is not divisible by seven. Along with the 146,000 days, (400 x 365 days), there are ninety-seven February 29s and Leap Year Days. The easiest way to explain how and why the Gregorian Calendar rotates during any 400-year cycle is that there are 365 days every year. Ninety-seven of the 400 years are Leap Years and contain a February 29; in them, there are 366 days. Years with 365 days have 52 weeks, with one additional day; years with 366 days have 52 weeks, with two additional days. Just add the additional days, after the fifty-two weeks, during all 400 years. The 97 Leap Years double to 194. Then add the other 303, and the overall total is 497. 97 plus 97 plus 303 equals 497. 497 days equals seventy-one weeks. Add the fifty-two weeks, in the four-hundred-year system of the Gregorian Calendar, (other than the 497 additional days), and there are 145,600 days, equalling 20,800 weeks. 145,600 days plus 497 days equals 146,097 days, which equals the 20,871 weeks and 146,097 days, listed above. Because of this, no chosen day of the month up to the 28th can occur the same number of times on each day of the week. The 13th day of the month is slightly more likely to be on a Friday than on any other day of the week
* Black Sabbath's self-titled debut album was released in the UK on Friday, February 13, 1970.
* Novelist Daniel Handler, also known as Lemony Snicket, released the 13th book of the Series of Unfortunate Events on Friday, October 13, 2006.
* January 13, 2006, and October 13, 2006, were not only Fridays, but the digits in the month, day, and year of each date add up to 13. This last occurred on October 13, 1520, and will next occur on May 13, 2011.
* There is an almost uncanny occurrence (at least in recent years) of the full moon falling on or very close to a Friday the 13th. July 13th, 1984, February 13th, 1987, March 13th, 1998, October 13th, 2000 were all full moons. June 13th, 2003 and January 13th, 2006 were the days before a full moon, and June 13th, 2014 and January 13th, 2017 occur slightly after the full moon. Friday, September 13th, 2019 will be the next year to contain a full moon on a Friday the 13th.
* The asteroid 99942 Apophis will make its close encounter on Friday, April 13, 2029.
* The Harry Potter Movie: Harry Potter and the Order of the Phoenix will be released on Friday, July 13, 2007.
* Hurricane Charley made landfall in Florida on Friday, August 13, 2004
Notable births on Friday the 13th
Georges Simenon - February 13, 1903
Sir Joh Bjelke-Petersen - January 13, 1911
Margaret Thatcher - October 13, 1925
Fidel Castro - August 13, 1926
T. J. Cloutier - October 13, 1939
Zoë Wanamaker - May 13, 1949
Peter Davison - April 13, 1951
Max Weinberg - April 13, 1951
Steve Buscemi - December 13, 1957
Julia Louis-Dreyfus - January 13, 1961
Will Clark - March 13, 1964
Tim Story - March 13, 1970
Michelle Sara Cox - December 13, 1974
Mary-Kate and Ashley Olsen - June 13, 1986
Marco Andretti - March 13, 1987
*From Wikipedia, the free encyclopedia