Why is April Fool's Day April 1st?

April Fool's Day originated from the story of a reform in France in the 16th century.

At that time, the old calendar was implemented in France. On April 1st, it was the New Year of the old calendar, and the French would exchange gifts in the New Year, wishing each other a happy New Year.

after the reformists proposed that the Gregorian calendar should be used as the calendar year, January 1st would be the New Year, but the conservatives were unwilling to give up the tradition of celebrating the New Year on April 1st and did not agree to start the new calendar year.

The reformists mocked these conservatives. On April 1st, they sent fake gifts and invited them to a fake reception, and called the deceived conservatives "April fools" or "fish on the hook". Since then, people have fooled each other on April 1 and become a popular custom in France. At the beginning of the 18th century, the April Fool's Day custom spread to Britain, and then it was brought to the United States by early British immigrants.