Opposite Day is celebrated on January 7th of each year. 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 to indicate that what was just asserted had the opposite meaning of what was originally intended (similar to the practice of crossed fingers to automatically nullify promises). Play has been compared to a children’s “philosophy course”, and the game has been used as an educational aid and suggested as preparation for “standardized testing”.on opposite day isn’t the opposite of opposite day regular day? but if the opposite of regular day is opposite day and the opposite of opposite day is regular day and the opposite of regular day is opposite day and the opposite of opposite day is regular day, and it keeps going and going and going. So on opposite i guess we will never really know what day it really is.