May 1: Beltane and Samhain in the Northern and Southern Hemispheres, respectively; Maharashtra Day in Maharashtra, India (1960); International Workers' Day, Law Day, Loyalty Day and National Day of Prayer (2025) in the United States Empire State Building 305 – Diocletian and Maximian retired as co-rulers of the Roman Empire, being succeeded by Galerius and Constantius Chlorus. 1794 – War of the Pyrenees: France regained nearly all the land it lost to Spain the previous year with its victory in the Second Battle of Boulou. 1931 – New York City's Empire State Building (pictured), at the time the tallest building in the world, opened. 1974 – Argentine president Juan Perón expelled Montoneros from a demonstration in the Plaza de Mayo in Buenos Aires, forcing the group to become a clandestine organization. Alexander William Williamson (b. 1824)Anna Jarvis (b. 1864)Eldridge Cleaver (d. 1998) More anniversaries: April 30 May 1 May 2 Archive By email List of days of the year About