ORIGIN: the exact origin of April Fool's Day isn't known, but many think it began in France around 1582 with the introduction of the Gregorian Calendar, which is the most widely used calendar today. In previous calendars, New Year's Day was between March 25 and April 1. Many people refused to change the New Year's celebration day and were dubbed "fools." They were sent on "fool errands," sent invitations to nonexistent parties and had other practical jokes played on them.
起源：四月愚人节的确切起源已不可考，不过很多人认为这个节日是起源于1582年前后的法国，在公历被引进之后——公历就是我们到今天还在使用的历法。在早先的历法中，新年是在3月25日和4月1日之间的。很多人不愿意改变新年的日子，就被叫做“愚人”。会有人给这些人发“愚人信”，发请帖请他们参加不存在的庆祝活动，还会成为恶作剧的对象。
HISTORY: The harassment evolved and spread to other countries, including Britian and Scotland. In England, jokes are only played in the morning as it is considered bad luck to play a practical joke on someone after noon.
历史：很快就席卷了其他国家，包括大不列颠和苏格兰。在英格兰，只有上午才能和人开玩笑，过了中午的恶作剧会被人认为是不吉利的。
The American colonies likely learned the tradition from the English and French.
美洲的殖民地可能是接受了英国和法国的传统。