The question of when April Fools Day began is shrouded in mystery, but the most widespread theory about its source involves the Gregorian calendar reform of the late sixteenth century. According to this theory observance of the day began in 1582, when France became the first country to switch from the Julian to the Gregorian calendar, following the directive of the pope. This switch meant that the beginning of the year was moved from the end of March to January 1. During the confusion of the change, those who persisted in celebrating he new year in April had various jokes played on them. For instance, pranksters would surreptitiously stick paper fish to their backs and taunt them with the name “Poisson d’Avril,” or “April Fish.” Thus, April Fools Day was born.
The calendar-change hypothesis might provide a reason why April 1 specifically became the date of the modern holiday, but it is clear that the idea of a springtime festival honoring pranks and mayhem had far more ancient roots. For instance, a rival French legend links spring prank-playing and the origin of the term “poison d’arvil” to the abundance of fish found in streams and rivers during early April. These young, newly hatched fish were easy to fool with a hook and lure. Therefore, the French called them “poison d’arvil” and celebrate this season of easy fishing by playing pranks on each other. It is still the custom in France to celebrate April Fools Day by eating chocolate fish. But even as far back as Roman times celebrations such as Hilaria honored spring mischief, while farther afield in India revelers observed Holi, the festival of color, and in northern Europe the festival of Lud, a Celtic god of humor, provided an excuse for merrymaking.
Anthropologists explain that the tradition to spring foolery relates to the transition from winter to spring. During such moments of seasonal transition, in that moment when winter passes away and spring begins, society is momentarily in a state of flux. It is as if the world holds is breath, waiting to see if the cycle of seasons will continue unbroken. In that moment of suspense, social rules are suspended and normal behavior does not govern. Raucous partying and trickery are briefly allowed. Other festivals marking moments of transition, such as New Year’s Eve, Halloween, and May Day, similarly involve partying and pranks.