Today is Friday the 13th, a date that has been considered unlucky in Western superstition for centuries. The fear of Friday the 13th even has a name: paraskevidekatriaphobia. Historians trace this belief back to a combination of the unlucky number 13—seen as unlucky because it follows the “perfect” number 12—and Friday, which was historically associated with bad luck and misfortune in some cultures. Over time, these ideas merged, giving rise to the modern superstition around this day.