| 104041 | September 12 | Event | 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) |
| 104042 | September 12 | Event | 1919 – Adolf Hitler joins the German Workers' Party (later the Nazi Party). |
| 104043 | September 12 | Event | 1923 – Southern Rhodesia, today called Zimbabwe, is annexed by the United Kingdom. |
| 104044 | September 12 | Event | 1930 – In cricket Wilfred Rhodes ends his 1110-game first-class career by taking 5 for 95 for H.D.G. Leveson Gower's XI against the Australians. |
| 104045 | September 12 | Event | 1933 – Leó Szilárd, waiting for a red light on Southampton Row in Bloomsbury, conceives the idea of the nuclear chain reaction. |
| 104046 | September 12 | Event | 1938 – Adolf Hitler demands autonomy and self-determination for the Germans of the Sudetenland region of Czechoslovakia. |
| 104047 | September 12 | Event | 1940 – Cave paintings are discovered in Lascaux, France. |
| 104048 | September 12 | Event | 1940 – An explosion at the Hercules Powder Company plant in Kenvil, New Jersey kills 51 people and injures over 200. |
| 104049 | September 12 | Event | 1942 – World War II: RMS Laconia, carrying civilians, Allied soldiers and Italian POWs is torpedoed off the coast of West Africa and sinks with a heavy loss of life. |
| 104050 | September 12 | Event | 1942 – World War II: First day of the Battle of Edson's Ridge during the Guadalcanal Campaign. U.S. Marines protecting Henderson Field on Guadalcanal are attacked by Imperial Japanese Army forces. |
| 104051 | September 12 | Event | 1943 – World War II: Benito Mussolini, dictator of Italy, is rescued from house arrest on the Gran Sasso in Abruzzi, by German commando forces led by Otto Skorzeny. |
| 104052 | September 12 | Event | 1944 – World War II: The liberation of Serbia from Nazi Germany continues. Bajina Bašta in western Serbia is among those liberated cities. Near Trier, American troops enter Germany for the first time. |
| 104053 | September 12 | Event | 1948 – Invasion of the State of Hyderabad by the Indian Army on the day after the Pakistani leader Muhammad Ali Jinnah's death. |
| 104054 | September 12 | Event | 1952 – Strange occurrences, including a monster sighting, take place in Flatwoods, West Virginia. |
| 104055 | September 12 | Event | 1953 – U.S. Senator and future President John Fitzgerald Kennedy marries Jacqueline Lee Bouvier at St. Mary's Church in Newport, Rhode Island. |
| 104056 | September 12 | Event | 1958 – Jack Kilby demonstrates the first integrated circuit. |
| 104057 | September 12 | Event | 1959 – Premiere of Bonanza, the first regularly scheduled TV program presented in color. |
| 104058 | September 12 | Event | 1959 – The Soviet Union launches a large rocket, Lunik II, at the moon. |
| 104059 | September 12 | Event | 1961 – The African and Malagasy Union is founded. |
| 104060 | September 12 | Event | 1964 – Canyonlands National Park is designated as a National Park. |
| 104061 | September 12 | Event | 1966 – Gemini 11, the penultimate mission of NASA's Gemini program, and the current human altitude record holder (except for the Apollo lunar missions) |
| 104062 | September 12 | Event | 1970 – Dawson's Field hijackings: Palestinian terrorists blow up three hijacked airliners in Jordan, continuing to hold the passengers hostage in various undisclosed locations in Amman. |
| 104063 | September 12 | Event | 1974 – Emperor Haile Selassie of Ethiopia, 'Messiah' of the Rastafari movement, is deposed following a military coup by the Derg, ending a reign of 58 years. |
| 104064 | September 12 | Event | 1974 – Juventude Africana Amílcar Cabral is founded in Guinea-Bissau. |
| 104065 | September 12 | Event | 1977 – South African anti-apartheid activist Steve Biko dies in police custody. |
| 104066 | September 12 | Event | 1979 – Indonesia is hit with an earthquake that measures 8.1 on the Richter scale. |
| 104067 | September 12 | Event | 1980 – Military coup in Turkey. |
| 104068 | September 12 | Event | 1983 – A Wells Fargo depot in West Hartford, Connecticut, United States, is robbed of approximately US$7 million by Los Macheteros. |
| 104069 | September 12 | Event | 1983 – The USSR vetoes a United Nations Security Council Resolution deploring the Soviet shooting down of a Korean civilian jetliner on September 1. |
| 104070 | September 12 | Event | 1984 – Dwight Gooden sets the baseball record for strikeouts in a season by a rookie with 246, previously set by Herb Score in 1954. Gooden's 276 strikeouts that season, pitched in 218 innings, set the current record. |