1940 is a year in the 20th century.
- August 20: In Mexico City, Leon Trotsky is assassinated by a Stalinist agent with an icepick. (TXF: "Musings of a Cigarette Smoking Man")
- In 1997, Melvin Frohike believed that August 20 was the birthdate of the Cigarette Smoking Man. This is based on the Cigarette Smoking Man's novels, Take a Chance: A Jack Colquitt Adventure and Second Chance: A Jack Colquitt Adventure, which Frohike believed was actually his autobiographies. (TXF: "Musings of a Cigarette Smoking Man")
- It should be noted that he could not have possibly been born in 1940, as this would conflict with him being seen as an adult in 1953, in the episode "Apocrypha."