May 1 is celebrated as International Workers' Day or Labor Day in many countries because of its historical connection to the labor movement and workers' rights. The date commemorates the Haymarket Affair of May 4, 1886, in Chicago, when police killed workers during a protest for the eight-hour workday. Though the fatal confrontation occurred on May 4, May 1 was chosen as the commemoration date because it was the date of the original labor demonstration.
The significance of May 1 as a labor holiday gained momentum internationally during the late 19th and early 20th centuries as the labor movement grew. Many countries adopted May 1 as an official holiday to recognize workers' contributions and advocate for workers' rights, including fair wages, safe working conditions, and reasonable working hours. Labor unions and workers worldwide use the day for parades, protests, and gatherings to draw attention to labor issues.
It's worth noting that not all countries observe May 1 as Labor Day. For example, the United States and Canada celebrate Labor Day in September, reflecting different historical contexts and labor movements in those nations. However, May 1 remains the primary international date for workers' celebrations and remains significant in countries across Europe, Asia, Latin America, and Africa. The day has evolved to represent broader concerns about workers' rights, economic justice, and fair treatment in the workplace.