May 1 is observed as International Labour Day in several countries to commemorate the labour movement which ushered in various reforms such as capping the work hours at eight and paid leaves. In India, Labour Day is referred to as Antarrashtriya Shramik Diwas or Kamgar Din.
Labour Day has its origins in the labour union movement in the United States.
At the peak of industrialisation at the beginning of the 19th Century, industrialists used to exploit the labour class and made them work up to 15 hours a day. The workers rose against this exploitation and demanded paid leaves, proper wages and breaks for the workforce.
The eight-hour day labour movement advocated eight hours for work, eight hours for recreation, and eight hours for rest. The Labour Day annually celebrates the achievements of these workers.
While the day has different orgins in different countries, the main reason for Labour Day is unfair treatment of the labour class.
May 1 was chosen to be International Workers' Day to commemorate the 1886 Haymarket affair in Chicago. In that year, on May 1, there was a general strike for the eight-hour workday. On May 4, the police acted to disperse a public assembly in support of the strike when an unidentified person threw a bomb. The police responded by firing at the workers. The event lead to several deaths.
In India, the first Labour day or May Day was celebrated in the year 1923. It was the Labour Kisan Party who had organised the May Day celebrations in Chennai (then Madras). One of these was organised at Triplicane Beach and the other one was arranged at the beach opposite Madras High Court.