Seven Things You Didn't Know About Friday The 13th

It's considered the unluckiest day on the calendar, associated with mishap, misfortune, mistake and just plain misery -- so beware of black cats!

Yes, in case you haven't noticed, today is Friday the 13th, so with that in mind, RadarOnline.com is taking a closer look at the mystique behind the infamous date, and how it came to be that way, with seven things you didn't know about Friday the 13th.

7. Yes there's a formal term: People who fear the day suffer from a condition doctors have labeled "Paraskevidekatriaphobia." The root of the word is a combination of Frigga (the Norse goddess who the day of the week is named for) and triskaidekaphobia, which means fear of the number 13.

President Franklin D. Roosevelt would not travel on the 13th day of any month and would never host 13 guests at a meal. Napoleon and Herbert Hoover were also triskaidekaphobic.

6. Baker's Dozen: One theory as to why 13 is considered a bad number is that 12 signifies wholeness for many things (clocks, months of the year, the tribes of Israel, Apostles of Jesus, constellations in the Zodiac), with 13 upsetting that balance. Experts estimate 85 percent of qualifying buildings do not designate a 13th floor (calling it the 14th floor, instead) because of the stigma attached to the number.

5. Unavoidable: Mathematicians have figured out that every calendar year will have at least one Friday the 13th. Next up, December 13, 2013.

4. Macabre Marketing Tool: Some have used the date's notoriety as a release date to further promote their projects, such as Black Sabbath's eponymous debut album (in the UK); the Friday the 13th films (five of 12 in the series);  and the 2012 horror movie, The Cabin in the Woods.

3.  Infamous Birthdays:  Butch Cassidy, the notorious American train and bank robber was born on Friday, April 13th, 1866, and Cuban dictator Fidel Castro was born on Friday, August 13th, 1926.

2. Fear Factor: North Carolina's Stress Management Center and Phobia Institute reported in 2004 that anywhere from 17 to 20 million Americans will alter their plans -- avoiding flights, work, and in extreme cases, leaving the house -- so as not to tempt fate on the allegedly unlucky day. The overall damage: $800-$900 million in lost revenues, the Institute said.