The date was chosen by a pan-national organization of socialist and communist political parties to commemorate the haymarket affair, which occurred in chicage on 4 May 1886. The 1904 sixth conference of the international, called on "all Social Democratic Party organisations and trade unions of all countries to demonstrate energetically on the First of May for the legal establishment of the 8 hours , for the class demands of the proletariat, and for universal peace

The first of May is a national public holidays in many countries worldwide, in most cases as "Labour Day", "International Workers' Day" or some similar name - although some countries celebrate a Labour Day on other dates significant to them, such as the United states, which celebrates Labour Day on the first Monday of September.

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 which occurs every year on May DAY (1 May), an ancient European spring festival.