May 1 is celebrated all over the world as International Labour Day. It's a celebration of labourers and the working class.
Labour Day, or Worker's Day as it is known in some countries is considered a public holiday. It was started in the commemoration of an incident that took place on May 4, 1886 at Chicago.
The incident popularly known as 'Haymarket affair', was a general assembly by people for an eight-hour work shift, which the police were trying to disperse, when suddenly an unidentified person threw a bomb at the police, to which the police retorted by opening fire at the crowds and killing four people.
Labour Day is promoted by the Labour Movement which is a movement for collective organisation of working people over the world, and implementation of labour laws. The movement sprang in Britain, during the Industrial Revolution which ultimately gave birth to the Labour Party.
International Labour Organisation (ILO), an agency of the United Nations deals with Labour issues and mainly works towards raising standards of labourers across the world. ILO celebrates Labour Day with rallies and demonstrations over the globe, and spreads awareness about the key issues it tackles, like eradicating forced labour, a demand for the minimum wage law, protecting the rights of migrant workers, among others.
— ILO (@ilo) May 1, 2014