What is Revenge of the 5th? The fifth of May is celebrated as the second Star Wars Day and is called Revenge of the 5th. It is used to celebrate the Dark Side, whereas May 4th is used to celebrate the Jedi. Because it immediately follows Star Wars Day, Revenge of the Fifth is supposed to be a day for fans to pass onto the Dark Side.

Source: http://www.hitc.com/en-gb/2021/05/04/revenge-of-the-5th/