April Fools’ Day (or All Fools Day) is celebrated on April 1, as the traditional day on which people play practical jokes on each other. April Fools’ Day has been celebrated for centuries in countries such as Britain and France. In ancient times, many cultures celebrated the beginning of the new year around April 1, shortly after the spring equinox. In the mid-sixteenth century Pope Gregory XIII, ordered that a new calendar—the Gregorian calendar—replace the old Julian calendar. The new calendar called for New Year’s Day to be celebrated on January 1. Many Protestant European countries refused to obey the pope’s order. France adopted the Gregorian calendar and shifted New Year’s Day to January 1, but many people refused to accept the new date or simply did not hear about the change. They continued to celebrate New Year’s on April 1. Other people teased these people, trying to trick them into believing other false stories. The custom of playing April Fools’ jokes was brought to the United States by the British. Today, people try to play good-natured tricks upon one another. When a victim believes a false story or is tricked, pranksters yell out “April Fool!”