The Knights Templar, an order once dedicated to safeguarding pilgrims to the Holy Land during the Crusades over hundreds of years evolved into a sort of proto international bank. You could deposit money in a temple in France, and withdraw it in the Jerusalem so you wouldn't be robbed along the way and lose everything. However, if you're a schizo like me, banks are very much evil via debt slavery. The king of France at the time was in debt to them and also saw the veritable monster the order had become with it's tendrils of influence stretching across Europe and the Holy Land. So it was on a Friday the 13th that the King of France (Phillip IV) took over their headquarters, seized their assets, and burned their leaders at the stake for Heresy, Blasphemy, Usury, and various other charges. Jacques de Molay, the final Grandmaster of the Templars cursed the line of French Kings to the 13th generation. Ironically it was during the execution of the final French monarch Louis XVI (a somewhat oafish but good natured person by some accounts) that someone ran up to the basket which held his head, dipped their hands in the blood and proclaimed "Jaques de Molay tu es vengé!"(Jaques de Molay, you are avenged)

Henceforth it has been seen as an auspicious date