Friday the 13th one occurrence each. A Friday the 13th occurs during any month that begins on a Sunday. 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"). The superstition surrounding this day may have arisen in the Middle Ages, "originating from the story of Jesus' last supper and crucifixion" in which there were 13 individuals present in the Upper Room on the 13th of Nisan Maundy Thursday, the night before his
Friday the 13th strengthen the superstition about Tuesday. In addition, in Greek the name of the day is Triti ("Τρίτη") meaning the third (day of the week), adding weight to the superstition, since bad luck is said to "come in threes". 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