May 11

Roman Emperor Constantine the Great dedicates the rebuilt city of Byzantium as "New Rome," establishing it as capital of the Eastern Roman Empire.

Roman Emperor Constantine the Great formally dedicated the rebuilt and expanded city of Byzantium as his new imperial capital, renaming it New Rome in an elaborate ceremony, though it would soon become popularly known as Constantinople in his honor. The city served as the seat of what developed into the Byzantine Empire for over a thousand years.

A printed copy of the Diamond Sutra is produced in China, regarded as the earliest dated printed book known to survive.

A copy of the Buddhist scripture known as the Diamond Sutra was printed in Dunhuang, China, using carved woodblock printing techniques, and it survives today, now held in the British Library, as the earliest dated printed book known to exist, predating Johannes Gutenberg's famous Bible by nearly six centuries.

Louis IX of France and James I of Aragon sign the Treaty of Corbeil, settling longstanding feudal territorial disputes.

King Louis IX of France and King James I of Aragon signed the Treaty of Corbeil, resolving longstanding feudal territorial and overlordship disputes between their respective kingdoms in the border regions of southern France and Catalonia, with each monarch renouncing competing claims to the other's core territories.

Ottoman naval forces defeat a Spanish fleet at the Battle of Djerba, marking the height of Ottoman Mediterranean naval power.

The Ottoman navy under the command of the formidable corsair Turgut Reis decisively defeated a combined Spanish, Genoese, and Papal fleet at the Battle of Djerba off the coast of Tunisia, capturing thousands of prisoners and marking the high point of Ottoman naval dominance across the Mediterranean Sea.

British Prime Minister Spencer Perceval is assassinated in the House of Commons, the only British prime minister ever killed in office.

British Prime Minister Spencer Perceval was shot dead in the lobby of the House of Commons by John Bellingham, a merchant nursing a personal financial grievance against the government over unresolved compensation claims. Perceval remains, to this day, the only British prime minister ever assassinated while in office.

Indian rebel soldiers seize Delhi from British control during the Indian Rebellion of 1857.

Rebelling Indian sepoy soldiers seized control of Delhi from British colonial authorities after marching from Meerut, a major early flashpoint that rapidly expanded into the widespread Indian Rebellion of 1857 against East India Company rule, an uprising that ultimately led Britain to dissolve the company and assume direct crown control over India.

Minnesota is admitted to the Union as the 32nd U.S. state.

Minnesota was admitted to the Union as the 32nd U.S. state, having developed rapidly through fur trading, timber harvesting, and agricultural settlement in the decades following its organization as a formal U.S. territory, drawing waves of Scandinavian and German immigrants to its fertile farmland.

IBM's Deep Blue defeats world chess champion Garry Kasparov, becoming the first computer to beat a reigning champion in a classic match format.

IBM's chess-playing supercomputer Deep Blue defeated reigning world champion Garry Kasparov in the deciding game of a six-game rematch, becoming the first computer system to beat a sitting world champion under standard tournament time controls, a landmark moment widely seen as a turning point in public perception of artificial intelligence.

Space Shuttle Atlantis launches on its final servicing mission to the Hubble Space Telescope.

Space Shuttle Atlantis launched on the fifth and final Hubble Space Telescope servicing mission, during which astronauts conducted a grueling series of challenging, high-risk spacewalks to repair failing components and install new scientific instruments, significantly extending the aging telescope's operational life well beyond its original planned lifespan.

David Cameron becomes British prime minister, forming the country's first coalition government since World War II.

David Cameron became British prime minister after leading the Conservative Party into a formal coalition government with the smaller Liberal Democrats party, following an inconclusive general election result. It was the first coalition government to govern the United Kingdom since the wartime national unity government of the Second World War.