Happy Secular Feast Day, Triskadekaphobes

We all know that the number 13 is said to be unlucky. Perhaps even more unlucky than the numeric sequence that Hurley played the lottery with before crashing on The Island. But why, specifically, the number 13? The staff at StraightDope.com says that we Christians are to blame:

"...13's stock dropped like a rock in the middle ages. The proximate cause of this apparently was the observation that Judas, the betrayer of Jesus, made 13 at the table. Other great medieval minds, I read here, pointed out that "the Jews murmured 13 times against God in the exodus from Egypt, that the thirteenth psalm concerns wickedness and corruption, that the circumcision of Israel occurred in the thirteenth year," and so on."

Fair enough. But why, specifically, is the combination of Friday and the number 13 considered especially unlucky? If you guessed Christianity again, you get a gold star courtesy of about.com:

Some say Friday's bad reputation goes all the way back to the Garden of Eden. It was on a Friday, supposedly, that Eve tempted Adam with the forbidden fruit. Adam bit, as we all learned in Sunday School, and they were both ejected from Paradise. Tradition also holds that the Great Flood began on a Friday; God tongue-tied the builders of the Tower of Babel on a Friday; the Temple of Solomon was destroyed on a Friday; and, of course, Friday was the day of the week on which Christ was crucified. It is therefore a day of penance for Christians.

In pagan Rome, Friday was execution day (later Hangman's Day in Britain), but in other pre-Christian cultures it was the sabbath, a day of worship, so those who indulged in secular or self-interested activities on that day could not expect to receive blessings from the gods — which may explain the lingering taboo on embarking on journeys or starting important projects on Fridays.

To complicate matters, these pagan associations were not lost on the early Church, which went to great lengths to suppress them. If Friday was a holy day for heathens, the Church fathers felt, it must not be so for Christians — thus it became known in the Middle Ages as the "Witches' Sabbath," and thereby hangs another tale.

As for me, I don't go in for superstition. I plan to celebrate this infortunate calendar confluence by dumping salt on the ground and throwing a black cat through a mirror.