April 1:

April 1 is the 91st day of the year (92nd in leap years) in the Gregorian calendar. There are 274 days remaining until the end of the year. April 1 is most notable in the Western world for being April Fools' Day.
April Fools' Day or All Fools' Day, although not a holiday in its own right, is a notable day celebrated in many countries on April 1. The day is marked by the commission of hoaxes and other practical jokes of varying sophistication on friends, family members, enemies, and neighbors, or sending them on fool's errand, the aim of which is to embarrass the gullible. Traditionally, in some countries, the jokes only last until noon: like UK, Australia, New Zealand and Canada, someone who plays a trick after noon is called an "April Fool". Elsewhere, such as in Ireland, France, and the USA, the jokes last all day. Another origin is that April 1 was counted the first day of the year in France. When King Charles IX changed that to January 1, some people stayed with April 1. Those who did were called "April Fools" and were taunted by their neighbors.