Most cultures have superstitions centred on the number thirteen. Let us start with a Greek word, which will impress your friends: Paraskevidekatriaphobia, meaning an irrational, even morbid, fear of Friday the 13th. Incidentally, you can trace the synonym friggatriskaidekaphobia to Frigga the goddess of Friday.

The word Paraskevidekatriaphobia was coined by therapist Dr Donald Dossey, in fact he claims whimsically that if you can pronounce the word then you are cured of the dreaded Friday 13th affliction

One famous study by Scanlon TJ, Luben RN, Scanlon FL, Singleton N. found that there were more car accidents on Friday February 13th than there were on Friday February 6th despite the fact that fewer people drove on February 13th. Guy is cynical, if you do enough studies you will find one that proves your point, their figures are 65 for Fri 13th, 45 for Fri 6th – not a big sample

Friday 13th Superstitions

It is bad luck to fall out of a thirteenth story window on Friday.
American Proverb

Do you believe that getting married on a Friday brings bad luck ?
Of course, why would Friday be an exception? Anon

http://www.guy-sports.com/humor/jokes/jokes_friday_13.htm#Paraskevidekatriaphobia_-_fear_of_Friday_13th_