1905 - Born on September 5th in Budapest. Hungarian-born writer-philosopher who focused on the disparity between reason and emotion as well as the problem of totalitarianism in the wake of the revolutions of the early 20th century.
1932 - Koestler was a member of the German Communist Party, but left the party during the Moscow trials.
1935 - Married to Dorothy Asher.
1945 - Became a naturalized American citizen.
1950 - Married to Mamaine Paget.
1965 - Married to Cynthia Jefferies Patterson.
1972 - Was the Commander of the British Empire.
1976 - In his book The Thirteenth Tribe, Koestler argues that the majority of European Jewry is actually descended from the Khazars, a Turkish power that existed in present-day Ukraine that in AD 740 converted to Judaism, eventually migrating westward to present-day Poland and Lithuania.
1980 - Koestler became one of the vice presidents of the Voluntary Euthanasia Society, EXIT.
1983 - Suffering from Parkinson's Disease and terminal Leukemia, Koestler committed suicide via drug overdose, accompanied by his wife.