May 1 (or May Day) is a more radicalized version of Labor Day in many countries. The date recalls Chicago’s Haymarket affair in 1886. American workers, tired of 18-hour days, staged a protest. Police eventually fired on the workers — killing eight. The following night, May 4, another rally turned violent when someone threw a bomb at police officers. An estimated 11 people died and scores more were injured. Communist and socialist political parties eventually chose May 1 as the date to honor the dead and injured workers.