The origins of the day are uncertain. Most people think it stems from Pope Gregory XIII. In 1582, he wanted his new Gregorian calendar to replace the old Julian Calendar. This called for New Year’s Day to be celebrated on January 1 instead of the end of March. But some people apparently didn't get the memo and continued to celebrate New Year’s Day on April 1. These poor folk were made fun of and were sent on ‘fools errands’ for a laugh.
However, others think April Fools' Day stems from the age when people used to hold spring festivals marking the end of winter with 'mayhem and misrule', according to the Museum of Hoaxes.
Ancient Romans held a festival known as Hilaria. The occasion was used to celebrate the resurrection of the god Attis. Hilaria, of course, resembles the word hilarity in English. The modern equivalent of Hilaria is called Roman Laughing Day.
Other non-Western cultures have their own traditions similar to April Fools’ Day as well. In India, Holi, a colorful Hindi festival that frequently entices non-Hindi participants to join in, often is celebrated by people playing jokes and throwing colorful dyes on each other.
Persian culture also has a holiday with a similar theme, known as Sizdahbedar. On this day, which typically coincides with April Fools’ Day itself, Iranians play pranks on one another.
Many other cultures have held renewal festivals in Europe around April 1 and there are references to these dating back to the 1500s. What is clear though is that by the 1700s, the day of hilarity was well entrenched in Britain, and now April 1 is officially the most amusing day of the year.
In modern times, people have gone to great lengths to create elaborate April Fools’ Day hoaxes. Newspapers, radio and TV stations and Web sites have participated in the April 1 tradition of reporting outrageous fictional claims that have fooled their audiences. In 1957, the BBC reported that Swiss farmers were experiencing a record spaghetti crop and showed footage of people harvesting noodles from trees; numerous viewers were fooled. In 1985, Sports Illustrated tricked many of its readers when it ran a made-up article about a rookie pitcher named Sidd Finch who could throw a fastball over 168 miles per hour. In 1996, Taco Bell, the fast-food restaurant chain, duped people when it announced it had agreed to purchase Philadelphia’s Liberty Bell and intended to rename it the Taco Liberty Bell. In 1998, after Burger King advertised a “Left-Handed Whopper,” scores of clueless customers requested the fake sandwich.