The vernal equinox, the first day of Spring, of 1583, and all subsequent years, occurred on or about March 21. The most common belief is that the observance of April Fool's Day began in France after the adoption of the reform calendar by Charles IX in 1564. When New Year's Day was changed to January 1. People who still celebrated New Year's Day on April 1 were the 'butt' of many jokes. In France it became customary to play tricks on family and friends.
French children fool their friends by taping a paper fish to their friends' backs.
In England, tricks can be played only in the morning. It lasts for two days there. The second day in Scotland is called Taily Day and is dedicated to pranks involving the buttocks. In Portugal, April Fool's is celebrated on the Sunday and Monday before Lent. The traditional trick there is to throw flour at your friends.