Paraskevidekatriaphobia
(pair.uh.skee.vee.dek.uh.tree.uh.FOH.bee.uh)

A morbid, irrational fear of Friday the 13th.

Therapist Dr. Donald Dossey, whose specialty is treating people with irrational fears, coined the term. He claims that when you can pronounce the word you are cured.

If you base your belief on media attention, superstition about Friday the 13th might be the number one superstition in America today. It appears, however, that only about 10% of us believe that Friday the 13th is an unlucky day.

Friday may be considered unlucky because Christ is thought to have been crucified on a Friday, which was execution day among the Romans. Yet, Christians don't call it Bad Friday. Friday was also Hangman's Day in Britain. Some even think that Friday was the day God threw Adam and Eve out of the garden of Eden, which is unlikely since the concept of Friday hadn't been invented yet.

Is Friday the 13th a particularly unlucky day?   It could be . . . if you believe it is.  Some prophecies are self-fulfilling.

http://skepdic.com/paraskevidekatriaphobia.html

More than 80 percent of high-rises do not have a 13th floor.
Many airports skip the 13th gate.
Airplanes have no 13th aisle.
Hospitals and hotels regularly have no room number 13.
Italians omit the number 13 from their national lottery.
On streets in Florence, Italy, the house between number 12 and 14 is addressed as 12 and a half.
Many cities do not have a 13th Street or a 13th Avenue
Many triskaidekaphobes, as those who fear the unlucky integer are known, point to the ill-fated mission to the moon, Apollo 13.