From Our Friends at Wikipedia: Friday the 13th occurs when the thirteenth day of a month falls on Friday, which superstition holds to be a day of good or bad luck. In the Gregorian calendar, this day occurs at least once, but at most three times a year. Any month’s 13th day will fall on a Friday if the month starts on a Sunday. In 2009 this applies to the months of February, March, and November. The next instance of this appears on the calendar for the year 2015. The fear of Friday the 13th is called paraskevidekatriaphobia.
A theory by author Charles Panati, one of the leading authorities on the subject of “Origins,” maintains that the Friday the 13th superstition can be traced back to ancient myth: “The actual origin of the superstition, though, appears also to be a tale in Norse mythology. Friday is named for Frigga, the free-spirited goddess of love and fertility. When Norse and Germanic tribes converted to Christianity, Frigga was banished in shame to a mountaintop and labeled a witch. It was believed that every Friday, the spiteful goddess convened a meeting with eleven other witches, plus the devil – a gathering of thirteen – and plotted ill turns of fate for the coming week. For many centuries in Scandinavia, Friday was known as ‘Witches’ Sabbath.’”
A further theory goes back to a combination of Paganism, Christianity, and the Battle of Hastings. For many, the number 13 was considered a lucky number, but with the efforts of Christianity attempting to degrade all things Pagan, they promoted 13 as an unlucky number, with Friday thus also being considered a bad day of the week. However, on Friday the 13th of October 1066, the decision was made by King Harold II to go to battle on Saturday the 14th of October, rather than allow his troops a day of rest (despite his army having made a long and arduous march from a battle near York just 3 weeks earlier). This decision in going to battle before the English troops were rested (the English lost and King Harold was killed), further established Friday the 13th as an unlucky day.
The Dutch Centre for Insurance Statistics (CVS) on June 12, 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 13th.
