April Fool's Day

Từ điển Oxford Advanced Learner 8th

April Fool’s Day [April Fools Day] (alsoApril Fools’ Day)BrE NAmE
1 April, the day when people in many countries play tricks or jokes on each other. The victim of the joke is called the April Fool. A typical trick is to make somebody believe something that is not true, e.g. that the clocks have changed and everything is an hour later, or that the government has announced an election. Newspapers, television and radio stations often join in with imaginary news stories.