Friday 13th

Does Friday the 13th freak you out? If so, hold on to your rabbit's foot extra tight, because there are three of these supposedly unlucky dates in 2012, though perhaps luckily, this Friday (July 13) is the last of them. Though, there's always some fear to be had next year, 2013.

Read on for 13 strange facts about this day of superstition.

1. This year is a special one for Friday the 13ths: There are three of them: Jan. 13, April 13 and July 13. The freaky thing? The dates fall exactly 13 weeks apart. That hasn't happened since 1984.

2. If that scares you, you may have paraskavedekatriaphobia (also known as friggatriskaidekaphobia). Those are the scientific terms for fear of Friday the 13th. Triskaidekaphobia is fear of the number 13.

3. It's not clear when or why Friday the 13th became associated with bad luck. The association may be biblical, given that the 13th guest at the Last Supper betrayed Jesus. His crucifixion was the next day, apparently a Friday. Or maybe 13 suffers from coming after the more-pleasing number 12, which gets to number the months, the days of Christmas and even the eggs in a dozen. (There are also 12 signs of the zodiac, 12 gods of Olympus, 12 labors of Hercules, 12 tribes of Israel and 12 apostles of Jesus.)

4. Whatever the reason, fear of 13 has spread far and wide: Hotels and hospitals often skip the 13th floor, and even airports quietly omit gate 13 sometimes.

5. The next year in which we'll have three Friday the 13ths is 2015. They'll fall in February, March and November.

6. If you think your Friday the 13th is likely to be bad, be glad you aren't a 14th-century Knight Templar. On Oct. 13, 1307, officers of King Philip IV of France raided the homes of thousands of these Crusades warriors, imprisoning them on charges of illegal activities. Though the charges weren't proven, more than a hundred died of terrible torture, according to "Tales of the Knights Templar"

7. Fittingly, director of psychological thrillers Alfred Hitchcock was born on the 13th — Friday, Aug. 13, 1999, would have been his 100th birthday. Perhaps aptly titled "Number 13," a film that was supposed to be Hitchcock's directorial debut never made it past the first few scenes and was shut down due to financial problems. He allegedly said the film wasn't very interesting. (Meanwhile, Fidel Castro was born on Friday the 13th, in August 1926.)

8. Why does the Friday the 13th superstition stick so firmly in our minds? According to Thomas Gilovich, who chairs the department of psychology at Cornell University, our brains are almost too good at making associations. "If anything bad happens to you on Friday the 13th, the two will be forever associated in your mind, and all those uneventful days in which the 13th fell on a Friday will be ignored," Gilovich said in a statement.

9. For pagans, 13 is actually a lucky number. It corresponds with the number of full moons in a year.

10. President Franklin D. Roosevelt is said to have avoided travel on the 13th day of any month, and would never host 13 guests at a meal. Napoleon and President Herbert Hoover were also triskaidekaphobic, with an abnormal fear of the number 13.

11. Mark Twain once was the 13th guest at a dinner party. A friend warned him not to go. "It was bad luck," Twain later told the friend. "They only had food for 12." Superstitious diners in Paris can hire a quatorzieme, or professional 14th guest. [13 Odd Occurrences on Friday the 13th]

12. Stock broker and author Thomas W. Lawson, in his 1907 novel "Friday the Thirteenth," wrote of a stockbroker's attempts to take down Wall Street on the unluckiest day of the month. Reportedly, stock brokers after this were as unlikely to buy or sell stocks on this unlucky day as they were to walk under a ladder, according to accounts of a 1925 New York Times article.

13. This fear of Friday the 13th can be serious business, according to the Stress Management Center and Phobia Institute in Asheville, N.C., which, among other things, offers therapy to help people overcome their fear of the freaky friday. Their estimates suggest hundreds of millions of dollars, up to $900 million are lost due to people's fear of flying or doing the business as usual that day, though that number isn't backed up with other estimates.