For most people, Friday the 13th is just another day on the calendar. However, for the superstitious, it is the unluckiest day of the year. The irrational fear of Friday the 13th is called friggatriskaidekaphobia. It affects over twenty million people in the US and many more worldwide. Some of the anxiety can be blamed on the namesake movie series. However, the day's bad reputation began long before the film's hockey-masked villain, Jason Voorhees, made his debut in 1980.