Saturday is April 1, or, as it is popularly called, Fools' Day. The holiday is celebrated by playing lighthearted pranks on family and friends. The origin of this fun tradition is unclear. Some believe it began in 1582 when France moved from the Julian calendar — which started the new year around April 1 — to the currently used Gregorian calendar. Anyone unaware that the new year now began on January 1 was pranked. Others think the custom began to celebrate the start of spring.