Well, it's Friday the 13th, the unluckiest day of the year. Even more unusual, this is the third such occurrence of the dreaded weekday this year, spaced exactly 13 weeks apart due to the leap year.

Math professor Tom Fernsler of the University of Delaware, (known as "Dr. 13" to his colleagues) told USA Today that this combination of phenomena will not happen again until 2040, when the days and weeks align in the favor of the phobia-inducing number 13. Typically, we get about one Friday the 13th every year; this year we have three.

If you're like most people in the United States, you maintain a healthy level of recreational superstition based on your cultural and religious upbringing. If you suffer from Paraskevidekatriaphobia, however, you're probably reading this while crying in a corner like a blubbering pile of neuroses, as this is the thing you fear most in the world.

For some, the phobia stems solely from the long-running series of horror movies starring the masked Jason Voorhees chopping up the lusty counselors at Camp Crystal Lake. However, the origins of the unlucky day stretch far back beyond the indulgent, sex-crazed 1980s. Death and fear have long been associated with the crazy prime number.

Many pagan goddess-worshipping religions revered the lunar cycle and the effect it had on the female body, so the number 13 was tied to femininity early on. Since all women were basically witches back then and their menstruation was something never to be trusted (duh), the early Church made it a number to also distrust. Of course, a classic coven of witches also required 13 members.

The early Church also believed that Fridays were the holy days for heathens, what they called "the Witches' Sabbath," so they made sure to take a break from all sorts of fun-having and meat-eating on Fridays to show those heathens what-for.

Thirteen people sat at the one-sided table at the Last Supper before Jesus was betrayed by Judas, and he was killed on a Friday. Similarly, in Norse mythology, the trickster god Loki (yep, that guy from The Avengers) showed up as the 13th uninvited guest to a banquet in Valhalla that led to the death of everyone's favorite warrior god, Balder.

Strangely, early Hindu texts also taught that it was "imperfect" for 13 people to gather together in any one place, especially for meals. So whomever came up with the story first really seemed to make an impact on the other storytellers...

The number 13 was associated with death in Egypt as well, as there are believed to be 13 stages of ascension in the afterlife. Because nobody knew what happened at that point, the destination was linked with trepidation and fear and, of course, death.

Ever since then, fear of the number has pervaded Western culture. Many architects and city planners avoid putting a 13th floor in their building designs. Many cities likewise skip over 13th Street or Avenue. In Turkey, the number is so despised that efforts were made to have the word removed from the nation's vocabulary.

Totally unrelated but interesting to note: Charles Manson, Jeffrey Dahmer and Theodore Bundy all have 13 letters in their names. Fidel Castro and Butch Cassidy were both born on a Friday the 13th. And Tupac Shakur died on September 13, 1996 . . . or did he?

Of course, a baker's dozen of donuts is also numbered at 13 and Friday is everyone's favorite day of the week otherwise, so can we really get that picky?