e/Opposite Day

Information
has gloss	eng: Opposite Day, also known as Opposites Day, is a word game where speech is modified so that meaning is inverted. Once Opposite Day is declared, statements mean the opposite of what they usually mean. Usually, a person would say, "After this phrase is over, it will be officially opposite day," and then Opposite Day will be officially started. Opposite Day can also be declared retroactively (after a statement) to indicate that the opposite meaning of what was said should be inferred. Opposite day games are usually played by schoolchildren.
lexicalization	eng: Opposite Day
instance of	c/Unofficial observances