April Fools' Day dates back centuries, but its origins remain unclear. A widespread theory is that it dates back to the adoption of the Gregorian calendar with the term April Fool applying to those who were still following the Julian Calendar.

　　愚人节已有数百年历史，但其来源仍存在争议。一种比较普遍的观点认为愚人节与“格里历”（即现行公历）的使用有关，当时人们将在公历普及后仍使用罗马儒略历（公历的前身）的人称为“四月愚人”。

　　By tradition in most countries, people can pull pranks before noon on April 1 in the name of April Fools' Day but become the fool if they do it in the afternoon.

　　按照大多数国家的传统，人们只能在愚人节的上午开愚人节玩笑。如果到了下午再去搞恶作剧，那么你自己就成了“愚人”了。

　　Vocabulary:

　　typeface：any design of type, including a full range of characters, as letters, numbers, and marks of punctuation, in all sizes（字体，打字机字体）

　　microchip：（计算机）微芯片

　　sequel：a literary work, movie, etc., that is complete in itself but continues the narrative of a preceding work（续集，续篇）