The holiday may also be known as Labour Day or International Worker's Day and is marked with a public holiday in over 80 countries, but there is a bloody story of how May Day became a Holiday for Workers. The 1 May date is used because in 1884 the American Federation of Organized Trades 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, a bomb exploded in the police ranks. It wounded 67 policemen, of whom seven died. The police opened fire, killing several men and wounding 200, and the Haymarket Tragedy became a part of U. S. history.