Today is a special day:
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 can be the case at least once every year, and up to three times a year. The superstition surrounding this day may have arisen in the Middle Ages.
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.