The United Kingdom officially declared war on Germany on August 4, 1914, thereby entering World War I.
The war in Europe officially ended with a German surrender on May 8, 1945.
You have to be a little more specific on which war you are talking about. World War I officially began on July 28, 1914. World War II officially began on September 1, 1939 (although some countries were already fighting, notably that Japan was already fighting China).
World War 2 officially started on 1 September 1939 when German troops invaded Poland. Austria and Czechoslovakia had been annexed by Germany before that date.
The signing of the Treaty of Versailles ended World War 1.
april,28,1914
April 6th 1917
in 1915
The United Kingdom officially declared war on Germany on August 4, 1914, thereby entering World War I.
May 8th 1945.
Germany invaded Poland on 1 September 1939, which is the official start date of World War 2, not World War 1
December 7, 1941
We entered the war in 1941 after the attack on Pearl Harbor. And then after we declared war on Japan, Germany and Italy declared war on us, officially starting WWII.
7th December, 1941. A date which will live in infamy --
Officially, when Japan attacked the US Pacific Fleet at Hawaii, December 7 1941.
Officially World War 2 ended 9/2/45 when the Allies and Japan signed The Instrument of Surrender on the USS Missouri.
The war in Europe officially ended with a German surrender on May 8, 1945.