International Workers' Day, also known as Labour Day in most countries and often referred to as May Day, is a celebration of labourers and the working classes that is promoted by the international labour movement and occurs every year on May Day (1 May). The first of May is a national, public holiday in many countries across the world, in most cases as "International Workers' Day" or a similar name. Some countries celebrate a Labour Day on other dates significant to them, such as the United States and Canada, which celebrate Labor Day on the first Monday of September.