Commemorating the 1886 Haymarket Affair in Chicago, International Workers’ Day is a celebration of the international labor movement. In 1886, a public assembly during a general strike in favor of the 8-hour workday was held. While police were attempting to disperse the participants, a bomb was thrown. Dozens of demonstrators were killed when police reacted by firing on the workers. The day is officially celebrated in over 80 countries around the world and unofficially by many others.