It can happen once or it can happen up to three time in one year... Friday the 13th. Why are so many people so afraid of today, basically Friday the 13th has been dubbed the day of bad luck. Some people don't even notice the day and some people are very frightened by it. In fact 17-21 million people in the US suffer from friggatriskaidekaphobia -the fear of Friday the 13th. Some people are so scared of the day that they take the day off and stay in bed. Retailers have reported an $800-$900 million loss in sales on days that land on Friday the 13th. Find out more info on the bad luck day here.