Opposite Day
Proper noun
Meaning
Opposite Day
(childish) A contrived holiday on which everything is done backwards, for example "yes" means "no".
Examples
There's a variety and depth to the song topics I get to write about in children's music and books: being able to write about things I wouldn't normally write about, like a disappointing pancake, or monsters or opposite day is really different than writing about heartbreak and relationships.
It’s always Opposite Day, I love that!
Opposite Day can be a whole lot of fun.
Can you imagine what life would be like as an adult if you could call Opposite Day whenever you wanted?
Opposite Day goes both ways, however, and Harden’s defense wound up being the difference in the end.