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,
twelve gods 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
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.
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.
There is at least one Friday the 13th in every year, and at the most there are three. In 2013, there are 2 Friday the 13ths: Friday the 13 of September and Friday the 13th of December
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 Paraskevà (meaning ''Friday''), and dekatreÃs (meaning ''thirteen'') attached to phobÃa.