Friday the 13th Superstitions....

Friday the 13th, 'the most widespread superstition'
The sixth day of the week and the number 13 both have foreboding reputations said to date from ancient times. It seems their inevitable conjunction from one to three times a year (there will be three such occurrences in 2012, exactly 13 weeks apart) portends more misfortune than some credulous minds can bear. According to some sources it's the most widespread superstition in the United States today. Some people refuse to go to work on Friday the 13th; some won't eat in restaurants; many wouldn't think of setting a wedding on the date.
How many Americans at the beginning of the 21st century suffer from this condition? According to Dr. Donald Dossey, a psychotherapist specializing in the treatment of phobias (and coiner of the term paraskevidekatriaphobia, also spelled paraskavedekatriaphobia), the figure may be as high as 21 million. If he's right, no fewer than eight percent of Americans remain in the grips of a very old superstition.
Exactly how old is difficult to say, because determining the origins of superstitions is an inexact science, at best. In fact, it's mostly guesswork.