What is celebrated every year by playing practical jokes and hoaxes?

April Fools' Day (sometimes called All Fools' Day) is celebrated every year on the 1st of April by playing practical jokes and spreading hoaxes. The jokes and their victims are called April fools. People playing April Fool jokes expose their prank by shouting "April Fool". Some newspapers, magazines, and other published media report fake stories, which are usually explained the next day or below the news section in small letters. Even if everyone is aware about the holiday, people tend to forget about it sometimes, which makes them believe in different nonsense presented in the official publications. Existing since the 19th century, the day is not a public holiday in any country, though many people are used to keeping with the traditions of this day.