But God hath chosen the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty. -
Although this day been observed for centuries in several countries, it is unclear how it began. It resembles other festivals, such as the Hilaria of ancient Rome (March 25) and the Holi festival of India (ending March 31). Its timing seems related to the Spring equinox (March 21), when nature "fools" mankind with sudden changes in the weather.
Probably the version we know goes back to sixteenth-century France, when the start of the new year was observed on April first. It was celebrated in much the same way as it is today with parties and dancing into the late hours of the night. In 1562, Pope Gregory introduced a new calendar for the Christian world, and the new year fell on January first. There were some people, however, who hadn't heard or didn't believe the change in the date, so they continued to celebrate New Year's Day on April first. Others played tricks on them and called them "April fools."
Is set apart for All Fools' Day.
But why the people call it so,
Nor I, nor they themselves do know.
But on this day are people sent
On purpose for pure merriment.
Poor Robin's Almanac (1790)