April 1 is April Fool's Day, or All Fools' Day. In many countries, including the United States and the United Kingdom, people play tricks on others on this day. A favourite joke is to send someone on a fool's errand (a search for something that does not exist), or to get people to believe ridiculous things. The victim is called an April Fool. No one knows where the April Fools' custom began.
The tradition originated in France and Great Britain.