<P> Friday the 13th is considered an unlucky day in Western superstition . It occurs when the 13th day of the month in the Gregorian calendar falls on a Friday, which happens at least once every year but can occur up to three times in the same year . In 2017, it occurred twice, on January 13 and October 13 . In 2018, it also occurs twice on April 13 and July 13 . There will be two Friday the 13ths every year until 2020, where 2021 and 2022 will have just one occurrence, in August and May respectively . </P> <P> The fear of the number 13 has been given a scientific name: "triskaidekaphobia"; and on analogy to this the fear of Friday the 13th is called paraskevidekatriaphobia, from the Greek words Paraskeví (Παρασκευή, meaning "Friday"), and dekatreís (δεκατρείς, meaning "thirteen"). </P>

Where does the superstition friday the 13th come from