Adolf Hitler orders extermination of mentally ill through the "T4 Euthanasia Program," arguing that wartime "was the best time for the elimination of the incurably ill"
In the "scoop of the century," Telegraph journalist Clare Hollingworth becomes the first to report the outbreak of World War II
- Last day of 1st-class cricket in England before the declaration of war against Germany; great slow left-armer Hedley Verity finishes with amazing figures of 7 for 9 v Sussex to give Yorkshire the County Championship
- Physical Review publishes 1st paper to deal with "black holes"
- Switzerland mobilizes its forces and the Swiss Parliament elects Henri Guisan to head the Swiss Army (an event that can happen only during war or mobilization)
- Switzerland proclaims neutrality at the outbreak of WWII
- The Wound Badge for Wehrmacht, SS, Kriegsmarine, and Luftwaffe soldiers is instituted. The final version of the Iron Cross was also instituted on this date
- World War II starts when Germany invades Poland by attacking the Free City of Danzig
- Heinrich "Heni" Messner, Austrian downhill skier (Olympic bronze 1968, 1972), born in Obernberg am Brenner, Austria
- Lily Tomlin, American comedienne and actress (9 to 5, Laugh-in, All of Me), born in Detroit, Michigan