April Fools Day

April Fools' Day (sometimes called All Fools' Day) is celebrated every year on April 1 by playing practical jokes and spreading hoaxes. The jokes and their victims are called April fools. People playing April Fool jokes expose their pranks 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.

From Wikipedia