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.
A Friday the 13th occurs during any month that begins on a Sunday.
So, why is Friday the 13th Unlucky?
According to biblical tradition, 13 guests attended the Last Supper, held on Maundy Thursday, including Jesus and his 12 apostles (one of whom, Judas, betrayed him). The next day, of course, was Good Friday, the day of Jesus’ crucifixion.
The irrational 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
According to the Stress Management Centre and Phobia Institute in Asheville, North Carolina, an estimated 17 to 21 million people in the United States are affected by a fear of this day, making it the most feared day and date in history. Some people are so paralysed by fear that they avoid their normal routines in doing business, taking flights or even getting out of bed. “It’s been estimated that [US]$800 or $900 million is lost in business on this day
In Spanish-speaking countries, instead of Friday, Tuesday the 13th (martes trece) is considered a day of bad luck.
In Spanish, the days of the week have their roots in Roman mythology and on the planets. Tuesday is considered dominated by the influence of Ares, the god of war (Mars in Roman mythology). The fall of Constantinople to the Fourth Crusade occurred on Tuesday, April 13, 1204.
Tuesday the 13th occurs in a month that begins on a Thursday.
In Italian popular culture, Friday the 17th (and not the 13th) is considered a day of bad luck. The origin of this belief could be traced in the writing of number 17, in Roman numerals: XVII. By shuffling the digits of the number one can easily get the word VIXI (“I have lived”, implying death in the present), an omen of bad luck.