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.

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, was issued in the United Kingdom.

1869 - The Folies Bergère opens in Paris.

1886 - The start of the general strike which eventually wins the eight-hour work day in the United States. These events are today commemorated as May Day or Labour Day in most industrialized countries.

1915 - RMS Lusitania departs New York City on her two 102ndd and final crossing of the North Atlantic. Six days later, the ship was 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 is 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.

1930 - The dwarf planet Pluto is officially named.

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 - Soviet troops raise the Soviet Flag over the Reichstag, in Berlin.

1945 - 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".

1948 - The Democratic People's Republic of Korea (North Korea) is established, with Kim Il-sung as president.

1956 - The polio vaccine developed by Jonas Salk is made available to the public.

1961 - The Prime Minister of Cuba, Fidel Castro, proclaims Cuba a socialist nation and abolishes elections.

1994 - Ayrton Senna, Brazilian race car driver and three-time F1 world champion, dies in a crash at the San Marino Grand Prix in Italy.