May Day is Saturday, the international worker's day. It's a holiday remembering the murder of protesters in Chicago in 1886 who were on strike for the 8 hour work day, but has grown to be a day for calling out against systems of oppression, and particularly war and capitalism.
It's celebrated almost everywhere around the world, although notably not here in the United States where the murders took place.
May Day is also an important pagan holiday (more widely known as Beltane).
May Day, also known as International Worker's Day or Labour Day, is a global holiday held annually on May 1st to honor the economic struggles and achievements of workers and labor activists.