When were WW I an WW II? (what year)?

World War 1 began in the year 1914 and officially ended in 1919

World War 2 began on September 1, 1939

- The war with Germany ended on May 8, 1945

- The war with Japan ended on August 15, 1945

WW I started on June 28, 1914 with the assassination of the Archduke of Austria-Hungary in Sarajevo. The U.S. did not get involved until 1917. The war ended as a matter of fact on November 11, 1918 when Germany signed an armistice agreement with England, France, and the United States and the shooting stopped. But legally, the war did not end until June 28, 1919, when the Treaty of Versailles was signed by all of the major powers of the world.

WW II formally started on September 1, 1939, when Germany seized Poland. It's best to point out that Germany had grabbed substantial territory before that (Austria in March of 1938 and Czechoslovakia in April of 1939), and that Japan began its invasion of China before that, in July of 1937. But Germany's taking of Poland triggered declarations of war across most of the world powers. Again, the U.S. did not get involved formally until December 7, 1941, when the Japanese bombed Pearl Harbor, Hawaii. The war ended in the European theater on May 7 and May 8, 1945, and in the Pacific Theater on August 15, 1945, after the United States detonated two nuclear bombs on Japan's home islands, the only time nuclear weapons have ever been used in war.

Here you go.