not a national holiday but a widely recognized day when
people play practical jokes and hoaxes on each other. It’s
believed that April Fool’s Day began with the reform of the calendar.
In 1582, Pope Gregory XIII ordered the advancement of the calendar by 10 days and introduced a new corrective device to curb further error: century years such as 1700 or 1800 would no longer be counted as leap years, unless they were (like 1600 or 2000) divisible by 400.
Since their inception, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals. When the Gregorian Calendar was introduced, the first day of the year came in a new month. So now, instead of on April 1st, New Year's Day was celebrated on January 1st.
Communication traveled slowly in those days, and some people did not learn of the change until several years later. And some were rebellious, refused to acknowledge the change, and
continued to celebrate the new year on April 1st. These people were labeled "fools” and were subject to ridicule, sent on "fool errands," or sent invitations to nonexistent parties, and had other practical jokes played upon them. This harassment evolved over time and a custom of prank-playing on April 1st has continued.
Have Happy Spring.