International Workers’ Day (also known as International Labour Day and May Day) is a holiday recognised by over 80 countries worldwide every year on May 1. The holiday commemorates what has become known as the Haymarket Affair in Chicago, USA in 1886.

Across the industrialised nations of the late 19th century, the working classes were increasingly protesting at the poor conditions and long hours imposed on them by employers, especially in factories. During a large-scale public protest in support of an eight-hour working day in Chicago in 1886, police were attempting to disperse the crowds when someone allegedly threw a bomb at the security forces. The police reacted by opening fire and killing many protestors and also some of their own officers.

On July 14 1889 in Paris, socialist and labour parties formed the Second International group and proposed 1 May 1890 as a day of international demonstration against the Haymarket Affair. May Day was formally recognised as an annual event at the International’s second congress in 1891.

In 1904, the International Socialist Conference meeting in Amsterdam called on “all Social Democratic Party organisations and trade unions of all countries to demonstrate energetically on May 1 for the legal establishment of the eight-hour day, for the class demands of the proletariat and for universal peace.” The congress made it “mandatory upon the proletarian organisations of all countries to stop work on May 1, wherever it is possible without injury to the workers”.

To this very day, May 1 has been embraced worldwide as a day of action for the working classes to demonstrate for improved employment conditions and social justice issues. Left-wing and communist governments have traditionally embraced the holiday with elaborate celebrations while right-wing and have fascist governments traditionally tried to repress it.

The United States and Canada however do not celebrate May 1 and instead have their Labour Day in September.  This is because the US President at the time of the Haymarket Affair, Grover Cleveland, did not want the date to be too strongly linked with the police killing of civilian workers. Although many US citizens, especially Hispanic-Americans, still demonstrate on May 1, the US government has always refused to change the official holiday date.

International Labour Day is recognised as an official national holiday in the Kingdom of Cambodia.