April Fools' Day, sometimes called All Fools' Day, is one of the most light hearted days of the year.

In 1582, Pope Gregory XIII ordered a new calendar (the Gregorian Calendar) to replace the old Julian Calendar. The new calendar called for New Year's Day to be celebrated Jan. 1. That year, France adopted the reformed calendar and shifted New Year's day to Jan. 1. According to a popular explanation, many people either refused to accept the new date, or did not learn about it, and continued to celebrate New Year's Day on April 1. Other people began to make fun of these traditionalists, sending them on "fool's errands" or trying to trick them into believing something false. Eventually, the practice spread throughout Europe.