It didn't. If you mean the starting date of World War 1 - it was 04 August 1914
August 4, 1914
They didn't.
6th April 1941
5/28/1935
1914
August 4 1914, after Germany did not withdraw from Belgium, Great Britain declared war on Germany.
Battle (Date)(victor) Battle of Waterloo (1815)(England and Dutch-Belgian troops) , the Battles of Ypres (WWI) (depends which battle), the Battle for Liège (1914 and 1940) (Germany), the Battle for the Yser river (Belgium), the Battle of the Golden Spurs (1302) (Flanders and Namur), the Battle of the Silver Helmets (1914) (Belgium), the Battle for Namur (1914 and 1940) (Germany) the Battle for Brussels (1830) (Belgium) ...
May 8, 1945
At 11.00 pm on 4th August 1914, Britain declared war on Germany. they joined the war to back up belgium when Germany broke their treaty and protect themselves.
Germany actually didn't invade Britain using Operation Sea Lion because he knew that he couldn't win because Hitler was scared to fight in water where he couldn't us blitzkrieg. So Hitler did not launch the operation at all.
There was never a real date the pact was supposed to last. Stalin knew that Germany would invade the Soviet Union, but he hoped they would invade some time around 1942 so that he could bring up his army in time.
Never. In World War 1 the Ottoman Turkish Empire was an ally of Germany. In World War 2 Turkey remained neutral, but in late January 1945 (!) made a nominal declaration of war on Germany.