Origins of April Fools Day
It is thought to have originated in the 16th century as a result of the adoption of the Gregorian calendar. Previously the New Year was celebrated the last week of March to coincide with the spring equinox, culminating on April 1. After the new calender was decreed many still celebrated the new year on April 1, either out of ignorance or stubborness. They subsequently became the subjects of jokes and objects of pranks amidst taunts of "April Fools".