September 12 is the 255th day of the year (256th in leap years) in the Gregorian calendar. There are 110 days remaining until the end of the year. This date is slightly more likely to fall on a Monday, Wednesday or Saturday (58 in 400 years each) than on Thursday or Friday (57), and slightly less likely to occur on a Tuesday or Sunday (56).

Events On this day...September 12

490 BC – Battle of Marathon: The conventionally accepted date for the Battle of Marathon. The Athenians and their Plataean allies, defeat the first Persian invasion force of Greece.
372 – Sixteen Kingdoms: Jin Xiaowudi, age 10, succeeds his father Jin Jianwendi as Emperor of the Eastern Jin dynasty.
1185 – Emperor Andronikos I Komnenos brutally put to death in Constantinople.
1213 – Albigensian Crusade: Simon de Montfort, 5th Earl of Leicester, defeats Peter II of Aragon at the Battle of Muret.
1229 – Battle of Portopí: The Aragonese army under the command of James I of Aragon disembarks at Santa Ponça, Majorca, with the purpose of conquering the island.
1309 – The First Siege of Gibraltar takes place in the context of the Spanish Reconquista pitting the forces of the Kingdom of Castile against the Emirate of Granada resulting in a Castilian victory.
1609 – Henry Hudson begins his exploration of the Hudson River while aboard the Halve Maen.
1634 – A gunpowder factory explodes in Valletta, Malta, killing 22 people and damaging several buildings.
1683 – Austro-Ottoman War: Battle of Vienna: Several European armies join forces to defeat the Ottoman Empire.
1814 – Battle of North Point: an American detachment halts the British land advance to Baltimore in the War of 1812.
1846 – Elizabeth Barrett elopes with Robert Browning.
1847 – Mexican–American War: the Battle of Chapultepec begins.
1848 – Switzerland approves its 1st Constitution and becomes a Federal state.
1857 – The SS Central America sinks about 160 miles east of Cape Hatteras, North Carolina, drowning a total of 426 passengers and crew, including Captain William Lewis Herndon. The ship was carrying 13–15 tons of gold from the California Gold Rush.
1885 – Arbroath 36–0 Bon Accord, a world record scoreline in professional Association football.
1890 – Salisbury, Rhodesia, is founded.
1897 – Tirah Campaign: Battle of Saragarhi.
1906 – The Newport Transporter Bridge is opened in Newport, South Wales by Viscount Tredegar.
1910 – Premiere performance of Gustav Mahler‘s Symphony No. 8 in Munich (with a chorus of 852 singers and an orchestra of 171 players. Mahler’s rehearsal assistant conductor was Bruno Walter)
1915 – French soldiers rescue over 4,000 Armenian Genocide survivors stranded on Musa Dagh.
1919 – Adolf Hitler joins the German Workers’ Party (later the Nazi Party).
1923 – Southern Rhodesia, today called Zimbabwe, is annexed by the United Kingdom.
1933 – Leó Szilárd, waiting for a red light on Southampton Row in Bloomsbury, conceives the idea of the nuclear chain reaction.
1938 – Adolf Hitler demands autonomy and self-determination for the Germans of the Sudetenland region of Czechoslovakia.
1940 – Cave paintings are discovered in Lascaux, France.

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