• 305 - Diocletian and Maximian retire from the office of Roman Emperor.
• 1328 - Wars of Scottish Independence end: Treaty of Edinburgh-Northampton – England recognises Scotland as an independent nation.
• 1576 - Stefan Batory, the reigning Prince of Transylvania, marries Anna Jagiellon and they become the co-rulers of the Polish-Lithuanian Commonwealth.
• 1707 - The Act of Union joins the Kingdom of England and Kingdom of Scotland to form the Kingdom of Great Britain.
• 1751 - The first cricket match is played in America.
• 1753 - Publication of Species Plantarum by Linnaeus, and the formal start date of plant taxonomy adopted by the International Code of Botanical Nomenclature.
• 1776 - Establishment of the Illuminati in Ingolstadt (Upper Bavaria), by Jesuit-taught Adam Weishaupt.
• 1778 - American Revolution: The Battle of Crooked Billet begins in Hatboro, Pennsylvania.
• 1785 - Kamehameha, the king of Hawaii defeats Kalanikupule and establishes the Kingdom of Hawaii.
• 1786 - Opening night of the opera The Marriage of Figaro by Wolfgang Amadeus Mozart in Vienna, Austria.
• 1834 - The British colonies abolish slavery.
• 1840 - The Penny Black, the first official adhesive postage stamp, is issued in the United Kingdom.
• 1846 - The few remaining Mormons left in Nauvoo, Illinois, formally dedicated the Nauvoo Temple.
• 1848 - The Fraternity of Phi Gamma Delta is founded at Jefferson College in Canonsburg, Pennsylvania.
• 1851 - The Great Exhibition opens in London by Queen Victoria.
• 1852 - The Philippine peso is introduced into circulation.
• 1863 - American Civil War: The Battle of Chancellorsville begins.
• 1869 - The Folies Bergère opens in Paris.
• 1884 - Proclamation of the demand for eight-hour workday in the United States.
• 1886 - The Haymarket Riots in Haymarket Square in Chicago, Illinois are the start of the general strike which eventually wins the eight-hour workday in the United States. These events are today commemorated as May Day or Labour Day in most industrialized countries.
• 1893 - The World's Columbian Exposition opens in Chicago.
• 1894 - Coxey's Army, the first significant American protest march, arrives in Washington, D.C.
• 1898 - Spanish-American War: The Battle of Manila Bay - the United States Navy destroys the Spanish Pacific fleet in the first battle of the war.
• 1900 - The Scofield mine disaster kills 200 in Scofield, Utah in what is to date the fifth-worst mining accident in United States history.
• 1901 - The Pan-American Exposition opens in Buffalo, New York.
• 1915 - The RMS Lusitania departs from New York City on her two hundred and second and final crossing of the North Atlantic. Six days later, the ship is torpedoed off the coast of Ireland with the loss of 1,198 lives, including 128 Americans, rousing American sentiment against Germany.
• 1925 - The All-China Federation of Trade Unions is officially founded. Today it's the largest trade union in the world, with 134 million members.
• 1927 - The first cooked meals on a scheduled flight are introduced on an Imperial Airways flight from London to Paris.
• 1927 - The Union Labor Life Insurance Company is founded by the American Federation of Labor.
• 1930 - The dwarf planet Pluto is officially named.
• 1931 - The Empire State Building is dedicated in New York City.
• 1940 - The 1940 Summer Olympics are cancelled due to war.
• 1941 - World War II: German forces launch Operation Mercury the largest airborne invasion to date in their bid to capture Crete.
• 1941 - World War II: German forces launch a major attack on Tobruk.
• 1945 - World War II: A German newsreader officially announces that Adolf Hitler has "fallen at his command post in the Reich Chancellery fighting to the last breath against Bolshevism and for Germany".
• 1946 - Start of 3 year Pilbara strike of Indigenous Australians.
• 1946 - The Paris Peace Conference concludes that the islands of the Dodecanese should be returned to Greece by Italy.
• 1948 - The Democratic People's Republic of Korea (North Korea) is established, with Kim Il-sung as president.
• 1950 - Guam is organized as a United States commonwealth.
• 1956 - The polio vaccine developed by Jonas Salk is made available to the public.
• 1956 - A doctor in Japan reports an "epidemic of an unknown disease of the central nervous system", marking the official discovery of Minamata disease.
• 1960 - Formation of the western Indian states of Gujarat and Maharashtra.
• 1960 - Cold War: U-2 Crisis – Francis Gary Powers, in a Lockheed U-2 spyplane, is shot down over the Soviet Union, sparking a diplomatic crisis.
• 1961 - The Prime Minister of Cuba, Fidel Castro, proclaims Cuba a socialist nation and abolishes elections.
• 1965 - Battle of Dong-Yin, a naval conflict between ROC and PRC, takes place.
• 1970 - Protests erupt in Seattle, Washington, following the announcement by U.S. President Richard Nixon that U.S. Forces in Vietnam would pursue enemy troops into Cambodia, a neutral country.
• 1971 - Amtrak (the National Railroad Passenger Corporation) is formed to take over U.S. passenger rail service.
• 1977 - 36 people are killed in Taksim Square, Istanbul, during the Labour Day celebrations.
• 1978 - Japan's Naomi Uemura, travelling by dog sled, becomes the first person to reach the North Pole alone.
• 1982 - The 1982 World's Fair opens in Knoxville, Tennessee.
• 1982 - Operation Black Buck begins. The RAF attack on the Argentine Air Force during Falklands War.
• 1983 - Greek composer Mikis Theodorakis is awarded the Lenin Peace Prize.
• 1987 - Pope John Paul II beatifies Edith Stein, a Jewish-born Carmelite nun who was gassed in the Nazi concentration camp at Auschwitz.
• 1989 - Disney-MGM Studios opens at Walt Disney World near Orlando, Florida, United States.
• 1991 - Rickey Henderson of the Oakland Athletics steals his 939th base, making him the all-time leader in this category. However, his accomplishment is overshadowed later that evening by Nolan Ryan of the Texas Rangers, when he pitches his seventh career no-hitter (breaking his own record).
• 1992 - On the third day of the 1992 Los Angeles riots, African-American activist, criminal, and victim of police beating Rodney King appears in public before television news cameras to appeal for calm and plead for peace, asking, "People, I just want to say, you know, can we all get along?".
• 1994 - Last day of the Spion Kop Grandstand at Liverpool F.C.'s Anfield stadium, perhaps the most famous stand in English Football.
• 1995 - Croatian forces launch Operation Flash during the Croatian War of Independence.
• 1997 - Tasmania becomes the last state in Australia to decriminalize homosexuality.
• 2000 - Philippine President Gloria Macapagal-Arroyo declares the existence of "a state of rebellion", hours after thousands of supporters of her arrested predecessor, Joseph Estrada, storm towards the presidential palace at the height of the EDSA III rebellion.
• 2003 - 2003 invasion of Iraq: In what becomes known as the "Mission Accomplished" speech, U.S. President George W. Bush declares that "major combat operations in Iraq have ended" on board the USS Abraham Lincoln off the coast of California.
• 2004 - Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia join the European Union, celebrated at the residence of the Irish President in Dublin.
• 2006 - The Puerto Rican government closes the Department of Education and 42 other government agencies due to significant shortages in cash flow.
• 2007 - The Los Angeles May Day mêlée occurs, in which the Los Angeles Police Department's response to a May Day pro-immigration rally become a matter of controversy.
• 2008 - The London Agreement on translation of European patents, concluded in 2000, enters into force in 14 of the 34 Contracting States to the European Patent Convention.

Births