1 Jan 1938: Fair Labor Standards Act A law was passed establishing a national minimum wage, a 40-hour work week, and prohibiting child labor.
2
1939
1 Jan 1939: World War II begins in Europe Germany invaded Poland, marking the start of World War II in Europe.
3
1940
1 Jan 1940: FDR reelected for third term Franklin D. Roosevelt became the first and only president to be elected to a third term.
4
1941
11 Mar 1941: Lend-Lease Act Congress passed a law allowing the U.S. to lend or lease war supplies to Allied nations.
7 Dec 1941: Attack on Pearl Harbor The Imperial Japanese Navy launched a surprise attack on the U.S. naval base at Pearl Harbor, Hawaii.
8 Dec 1941: U.S. declares war on Japan The United States officially entered World War II.
5
1942
1 Jan 1942: Declaration by United Nations Representatives of 26 Allied nations signed a declaration to fight against the Axis powers.
19 Feb 1942: Japanese-American internment President Roosevelt signed an executive order authorizing the internment of Japanese Americans.
25 Feb 1942: Battle of Los Angeles A rumored air raid on Los Angeles led to a panicked anti-aircraft barrage, though no enemy planes were ever found.
4 Jun 1942: Battle of Midway The U.S. Navy defeated the Imperial Japanese Navy at the Battle of Midway, a turning point in the Pacific War.
6
1943
1 Jan 1943: War Production Board The U.S. government took control of industries to produce war materials.
7
1944
1 Jan 1944: Servicemen's Readjustment Act (G.I. Bill) A law that provided benefits to World War II veterans, including low-cost mortgages and tuition assistance.
6 Jun 1944: D-Day Invasion Allied forces launched a massive amphibious invasion of Normandy, France, beginning the liberation of Western Europe.
17 Dec 1944: Battle of the Bulge begins The German army launched a surprise counteroffensive in the Ardennes region of Belgium.
8
1945
20 Jan 1945: FDR's fourth inauguration Franklin D. Roosevelt was sworn in for an unprecedented fourth term.
4 Feb 1945—11 Feb 1945: The leaders of the U.S. and Soviet Union met to discuss the post-war reorganization of Europe.
12 Apr 1945: FDR dies President Franklin D. Roosevelt died in office; Harry S. Truman became president.
28 Apr 1945: Mussolini executed Italian dictator Benito Mussolini was captured and executed.
30 Apr 1945: Hitler commits suicide Adolf Hitler committed suicide in his Berlin bunker.
8 May 1945: V-E Day (Victory in Europe) The Allied forces celebrated the unconditional surrender of Nazi Germany.
26 Jun 1945: United Nations Charter signed The United Nations Charter was signed in San Francisco, officially creating the organization.
16 Jul 1945: First atomic bomb test (Trinity) The first detonation of a nuclear weapon occurred in the New Mexico desert.
17 Jul 1945—2 Aug 1945: The leaders of the U.S. and Soviet Union met to decide the future of Germany.
6 Aug 1945: Atomic bomb dropped on Hiroshima The U.S. dropped an atomic bomb on the Japanese city of Hiroshima.
8 Aug 1945: Soviets declare war on Japan The Soviet Union declared war on Japan and invaded Manchuria.
9 Aug 1945: Atomic bomb dropped on Nagasaki A second atomic bomb was dropped on the city of Nagasaki, Japan.
14 Aug 1945: V-J Day (Victory over Japan Day) Japan announced its unconditional surrender, effectively ending World War II.
2 Sep 1945: Formal Japanese surrender Japanese officials formally signed the instrument of surrender aboard the USS Missouri in Tokyo Bay.