April Fool's Pranks--one answer
How the custom of April Fool pranking came about remains shrouded in mystery.
When the western world employed the Julian calendar, years began on March 25. Festivals marking the start of the New Year were celebrated on the first day of April because March 25 fell during Holy Week. The adoption of the Gregorian calendar during the 1500s moved the New Year to January 1. According to the most widely believed origin postulated for April Fools’ Day, those who could be tricked into believing April 1 was still the proper day to celebrate the New Year earned the sobriquet of April fools. To this end, French peasants would unexpectedly drop in on neighbors on that day in an effort to confuse them into thinking they were receiving a New Year’s call. Out of that one jape supposedly grew the tradition of testing the patience of family and friends.
But that’s only one theory. There are more.





