I stumbled upon an article I’d posted a couple years ago about “Friday the Thirteenth” and thought I’d again share some of what I learned about the subject. At least a few of you, I’m sure, believe the day to be unlucky while others of you believe it to be nothing more than superstitious folklore. Regardless, it is what it is and, right or wrong, some folks take it quite seriously. Here are a few factoids:

A Friday occurring on the 13th day of any month is considered to be a day of bad luck in English and Portuguese-speaking cultures around the globe. The fear of Friday the 13th is called paraskavedekatriaphobia. (Say that three times quickly!) Months whose first day falls on a Sunday will contain a Friday the 13th. (Didn’t know that, did you!)

The first recorded incident relating to Friday the 13th refers to the massacre of the Knights Templar on Friday, October 13, 1307. Pope Clement V viewed the Templar as a threat, so he decreed that they be eliminated. The Vatican was not directly involved in the massacre, but rather acted through King Philip IV of France. Philip sent letters to his forces all over the country with instructions to seek out and arrest all known members of the Knights, slaughter those that resisted, and capture Jacques DeMolay, the last known Grand Master of the Knights Templar.

Another possible origin relates to the Last Supper. Judas, the thirteenth guest, was instrumental in the Crucifixion of Jesus, which is believed to have happened on a Friday. Other theories suggest that Eve offered the apple to Adam on a Friday or the slaying of Abel happened on a Friday.

Some people are so paralyzed by fear that they’re 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. A British Medical Journal study has shown that there is a significant increase in traffic related accidents on Friday the 13ths. (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.)

An interesting side note: In the Spanish-speaking world, it is Tuesday the 13th (as well as Tuesdays in general) that brings bad luck; a Spanish proverb reads, “En martes, ni te cases ni te embarques.” (On Tuesday, neither get married nor start a journey.)

Those of you who believe in this sort of thing won’t be happy to learn that this is first of three occurrence of Friday the Thirteenth this year—the others occur in March and November. But we can relax a little in 2010 which has just one—in August. The chart on the right will help remind you which days to stay in bed, at least during the current 28 year cycle.

So, is Friday the thirteenth really unlucky or is this belief just a hangover from the time when the patriarchal, male-centered religion of Christianity was trying to differentiate itself from and destroy its ancient, pagan, goddess-loving competitors? Decide for yourself. You can learn more about Friday the thirteenth here, here and here. And no, none of the preceding material was sourced from Dan Brown’s fictional novel The Da Vinci Code. No, not the movie, either. Really.