April Fools’ Day is believed to be linked to the adoption of the Gregorian calendar within Europe in 1582, as this change officially moved New Year’s Day to January 1st annually. Because some Europeans (primarily non-Catholic) continued to use the Julian calendar to celebrate the antiquated late March New Year of the Indo-European tradition, they were teased as “fools” for being out of date. In France, the custom of affixing paper fish to the backs of others, a tradition referred to as “poisson d’avril” which means “April fish” in French, helped the tradition of pranks and jokes being played upon April 1st spread across Europe and eventually the wider world. The French tradition is to secretly attach paper fish upon the back of another person and then shout “April Fish!” in a playful way once discovered by said victim. Although the true origin of April Fools and its relation to pranks and jokes is still contested during the modern day, the shifting of Catholic European countries to the Gregorian calendar in 1582 remains the most coherent explanation