1940

align="center" colspan=2 | Years:
1937 1938 1939 - 1940 - 1941 1942 1943

align="center" colspan=2 | Decades:
1910s 1920s 1930s - 1940s - 1950s 1960s 1970s

align="center" | Centuries:
19th century - 20th century - 21st century

1940 was a leap year starting on Monday (link will take you to calendar).

Events

January-February

January 5 - FM radio is demonstrated to the FCC for the first time.
January 6 - World War II: Mass execution of Poles, committed by Germans in the Poznan, Warthegau.
January 12 - World War II: Russia bombs cities in Finland.
February 2 - Frank Sinatra debuts with the Tommy Dorsey orchestra
February 2 - The Complex Number Calculator, a calculator for complex arithmetic based on relays, was completed. (see History of computing hardware).
February 2 - The first transposons are discovered in maize (Zea mays, aka corn) by Barbara McClintock.
February 11 - Japan celebrates the 2, 600th anniversary of the ascension of first Emperor Jimmu to the Chrysanthemum Throne. A number of prisoners receive early release, notably including former prostitute and later actress Sada Abe.
February 21 - James Wong, famous composer of Hong Kong (d. November 24, 2004.)
February 23 - World War II: Soviet Union troops conquer Lasi Island.
February 29 - For her role as Mammy in Gone with the Wind, Hattie McDaniel becomes the first African American to win an Academy Award (Best Supporting Actress).

March-April

March 3 - In Sweden, a time bomb destroys the office of Norrskenflamman newspaper of Swedish communists - 5 dead
March 5- Members of Soviet politbiuro: Stalin, Molotov, Lazar Kaganovich, Mikhail Kalinin, Kliment Voroshilov and Lavrenty Beria himself, signed prepared by Beria order of execution of 25,700 Polish intelligentsia, including 14,700 Polish POW, known also as Katyn massacre.
March 12 - Soviet Union and Finland sign a peace treaty in Moscow ending the Winter War. Finns, and the World opinion, shocked by the harsh terms.
March 18 - World War II: Axis powers - Adolf Hitler and Benito Mussolini meet at Brenner Pass in the Alps and agree to form an alliance against France and the United Kingdom.
April 7 - Booker T. Washington becomes the first African American to be depicted on a United States postage stamp.
April 9 - World War II: Germany invades Denmark and Norway in operation Weserbung. The British campaign in Norway is simultaneously commenced.

May

May 9 - World War II: German submarine U-9 sinks French coastal submarine Doris near Den Helder.
May 10 - World War II: Germany invades Belgium, the Netherlands, and Luxembourg.
May 13 - World War II: Nazi Germany's conquest of France begins as the German army crosses the Meuse River.
May 14 - World War II: The Dutch city of Rotterdam is bombed by the German Luftwaffe.
May 14 - World War II: The Netherlands surrender to Germany.
May 15 - World War II: German troops occupy Amsterdam and invade Northern France.
May 15 - Nylon stockings go on sale for the first time in the United States.
May 15 - Opening Day for the first McDonald's restaurant, established by brothers Dick and Mac McDonald in San Bernardino, California, USA.
May 17 - World War II: Germany occupies Brussels, Belgium
May 20 - Holocaust: The first prisoners arrive at a new concentration camp at Auschwitz.
May 24 - Igor Sikorsky performs the first successful single-rotor helicopter flight.
May 25 - World War II: The Battle of Dunkirk begins.
May 26 - World War II: Battle of Dunkirk - In France, Allied forces begin a massive evacuation from Dunkirk.
May 28 - World War II: Belgium surrenders to Germany.

June

June 4 - World War II: Dunkirk evacuation ends - British forces complete evacuating 300,000 troops from Dunkirk in France.
June 9 - World War II: The British Commandos are created.
June 10 - World War II:- Italy declares war on France and the United Kingdom.
June 10 - World War II: German forces, under General Erwin Rommel, reach the English Channel.
June 10 - World War II: Canada declares war on Italy.
June 10 - World War II: Norway Surrenders to German forces.
June 12 - World War II: 13,000 British and French troops surrender to Field Marshal Erwin Rommel at St. Valery-en-Caux.
June 14 - World War II: Paris falls under German occupation.
June 14 - World War II: U.S. President Franklin D. Roosevelt signs the Naval Expansion Act into law which aims to increase the United States Navy's tonnage by 11 %.
June 14 - Holocaust: A group of 728 Polish political prisoners from Tarnw become the first residents of the Auschwitz concentration camp.
June 17 - The three Baltic states of Estonia, Latvia and Lithuania fall under the occupation of the Soviet Union.
June 17 - World War II: Operation Ariel begins - Allied troops start to evacuate France, following Germany's takeover of Paris and most of the nation.
June 17 - World War II: Sinking of the RMS Lancastria by the Luftwaffe near Saint-Nazaire, France.
June 23 - World War II: German leader Adolf Hitler surveys newly defeated Paris in now occupied France.http://history1900s.about.com/library/holocaust/blhitler38.htm

July-August

July 5 - World War II: The United Kingdom and the Vichy France government break off diplomatic relations.
July 10 - World War II: Vichy France government established.
July 10 - World War II: Battle of Britain. Luftwaffe, the Air Force of Germany, in preparation for Operation Sealion begins to hit British convoys in the English Channel thus starting the battle (this start date is contested, though).
July 14 - World War II: Andrew George Latta McNaughton takes command 7th Army Corps consisting of British, Canadian and New Zealand troops.
July 21 - Estonia, Latvia and Lithuania are proclaimed to be "independent" Socialist republics.
August 3 - Lithuania is officially incorporated in the Soviet Union as the Lithuanian SSR.
August 5 - Latvia is officially incorporated in the Soviet Union as the Latvian SSR.
August 6 - Estonia is officially incorporated in the Soviet Union as the Estonian SSR.
August 20 - Ramn Mercader assassinates exiled Russian revolutionary Leon Trotsky in Mexico City with an ice-ax. Trotsky dies the next day.

September-October

September 4 - World War II: The USS Greer becomes the first United States ship fired upon by a German submarine in the war, even though the United States is a neutral power. Tension heightens between the two nations as a result.
September 7 - Treaty of Craiova: Romania loses Southern Dobrudja to Bulgaria.
September 7 - World War II: The Blitz - Nazi Germany begins to rain bombs on London. This will be the first of 57 consecutive nights of strategic bombing.
September 12 - The Hercules Munitions Plant in Kenvil, New Jersey explodes, killing 55 people.
October 9 - World War II: Battle of Britain - During a nighttime air raid by the German Luftwaffe, St. Paul's Cathedral is pierced by a bomb; Musician John Lennon is born during an air-raid in Liverpool, England.
October 15 - First release of The Great Dictator, directed by Charlie Chaplin who is cast as fascist dictator Adenoid Hynkel, clearly modeled on Fhrer Adolf Hitler of Nazi Germany.
October 28 - World War II: Italy invades Greece.
October 31 - World War II: Battle of Britain ends - The United Kingdom prevents Germany from invading Britain.

November

November 1 - French children discover Lascaux caves
November 5 - U.S. presidential election, 1940: Democrat incumbent Franklin D. Roosevelt defeats Republican challenger Wendell Willkie and becomes the United States' first third-term president.
November 7 - In Washington, the middle section of the Tacoma Narrows Bridge collapses in a windstorm, a mere four months after the bridge's completion (it opened to traffic on July 1, 1940 as the third-longest suspension bridge in the world).
November 11 - World War II: Battle of Taranto - The Royal Navy launches the first aircraft carrier strike in history, on the Italian fleet at Taranto.
November 11 - World War II: The German Hilfskreuzer (cruiser) Atlantis captures top secret British mail, and sends it to Japan
November 11 - Armistice Day Blizzard: An unexpected blizzard kills 144 in U.S. Midwest.
November 14 - World War II: In England, the city of Coventry is destroyed by 500 German Luftwaffe bombers (150,000 fire bombs, 503 tons of high explosives, 130 parachute mines leveled 60,000 of the city's 75,000 buildings; 568 people were killed).
November 16 - World War II: In response to Germany leveling Coventry two days before, the Royal Air Force begins to bomb Hamburg (by war's end, 50,000 Hamburg residents died from Allied attacks).
November 18 - World War II: German leader Adolf Hitler and Italian Foreign Minister Galeazzo Ciano meet to discuss Benito Mussolini's disastrous invasion of Greece.
November 20 - World War II: Hungary, Romania and Slovakia join the Axis Powers.
November 27 - In Romania, coup leader General Ion Antonescu's Iron Guard arrests and executes over 60 of exiled king Carol II of Romania's aides. Among the dead is former minister and acclaimed historian Nicolae Iorga.