The oldest known “April Fools’ Day” type tradition, Sizdah Bedar, can be found in Iran and has been going on since around 500 BC. The event is simply a ceremony of sorts where people go spend the day outside and have a picnic. It is also traditional for people to play pranks on one another during the day. This celebration usually happens on April 1st, but can occasionally occur on April 2nd.
April Fish! In certain countries, such as Belgium, France, and Italy, it is a tradition, particularly among children, to try to tape little fish-cutouts on people’s backs without them knowing and then shout “April Fish!” (obviously not in English ;-)). The earliest reference to “April Fish” seems to be from around the 16th century from Eloy d’Amerval, a French poet....
History of April Fools Day.