International Workers' Day
International Workers' Day, also known as Labour Day in some countries and often referred to as May Day, is a celebration of labourers and the working classes that is promoted by the international labour movement and occurs every year on May Day.
The date had been chosen by the American Federation of Labor to continue an earlier campaign for the eight-hour day in the United States, which had culminated in the Haymarket affair, which occurred in Chicago on 4 May 1886.
May Day subsequently became an annual event.