According to British historians, according to the encyclopedia of the English, April fool's day is a lie festival that appeared after the religious revolution in the 15th century.
At that time, Philip ii, king of Spain, established a heresy tribunal. Anyone who was not a Catholic was considered a heresy and was sentenced to death on April 1 every year.
The subjects were so frightened that they told lies and made fun of them every day to dilute their fear and hatred of the ruler. Since then, continue to use for a long time, evolved into today's April fool's day.
译文：
据英国历史学家的考证：英人百科全书里面则是记载着：“愚人节”乃是公元十五世纪宗教革命之后始出现的一个说谎节日。
那时西班牙王腓力二世曾经建立一个“异端裁判所”，只要不是天主教徒就被视为异端，在每年四月一日处以极刑，也就是死刑。
臣民们感到非常恐怖，于是每天以说谎取笑为乐，来冲淡对统治者之恐惧与憎恨。其后，沿用日久，演变为今日之“愚人节”。