The eleventh hour of the eleventh day of the eleventh month, 1918.
Now known as Veterans' Day, Armistice Day began as the celebration of "the war to end all wars" in 1918.
One of the most famous of all poems, and one written during The World War is titled, "In Flanders Fields" by Lieutenant Colonel John McCrae, M.D.
It is well worth another read.
http://www.arlingtoncemetery.net/flanders.htm