International Workers' Day (also known as May Day) is a celebration of the international labour movement and left-wing movements. It commonly sees organized street demonstrations and marches by working people and their labour unions throughout most of the world. May 1 is a national holiday in more than 80 countries. It is also celebrated unofficially in many other countries.
International Workers' Day is the commemoration of the 1886 Haymarket Massacre in Chicago, when Chicago police fired on workers during a general strike for the eight hour workday, killing several demonstrators and resulting in the deaths of several police officers, largely from friendly fire. In 1889, the first congress of the Second International, meeting in Paris for the centennial of the French Revolution and the Exposition Universelle, following a proposal by Raymond Lavigne, called for international demonstrations on the 1890 anniversary of the Chicago protests. May Day was formally recognized as an annual event at the International's second congress in 1891.
In many countries, the working classes sought to make May Day an official holiday, and their efforts largely succeeded. May Day has long been a focal point for demonstrations by various socialist, communist and anarchist groups. In some circles, bonfires are lit in commemoration of the Haymarket martyrs, usually at dawn. May Day has been an important official holiday in Communist countries such as the People's Republic of China, Cuba and the former Soviet Union. May Day celebrations typically feature elaborate popular and military parades in these countries. (From: Wikipedia)