Day or International Worker’s Day.
The 1 May date is used because in 1884 the American Federation of Organized Trades and Labor Unions demanded an eight-hour workday, to come in effect as of 1 May 1886. This resulted in the general strike and the Haymarket Riot of 1886, but eventually also in the official sanction of the eight-hour workday.
1 May is celebrated as May Day in most countries around the world. In the United Kingdom the bank holiday isn’t fixed at May 1st, but instead is observed on the first Monday of May.
In the 20th century, the holiday received the official endorsement of the Soviet Union, and it is also celebrated as the Day of the International Solidarity of Workers, especially in some Communist states. Celebrations in communist countries during the Cold War era often consisted of large military parades with the latest weaponry being exhibited as well as shows of common people in support of the government.
1 May was also a pagan holiday in many parts of Europe, Its roots as a holiday stretch back to the Gaelic Beltane. It was considered the last day of winter when the beginning of summer was celebrated.
During Roman times, 1 May was seen as a key period to celebrate fertility and the arrival of spring. The Roman festival of Flora, the goddess of flowers and the season of spring, was held between 28 April and 3 May.