September 12 is the 255th day of the year (256th in leap years). There are 110 days remaining.
- 1953: Nikita Krushchev was elected as the first secretary of the Communist Party of the Soviet Union.
- 1953: US Senator John F. Kennedy married Jacqueline Lee Bouvier.
- 1983: Arnold Schwarzenegger became a US citizen.
- 1992: Dr. Mae Carol Jemison became the first African-American woman in space.