Today is known as Armistice Day.
In the First World War, the Armistice sought by the Germans from the Allies came into force on November 11, 1918 and ended all fighting in that war. The Armistice had to be renewed three times before the Allied peace terms were finally presented to the Germans on May 7, 1919.
During the period 1919-38, the date "November 11" was kept as Armistice Day (also known as Poppy Day and Remembrance Day) when two minutes silence was observed throughout the British Commonwealth, starting at 11 am.
The ceremony lapsed during the Second World War but was resumed in 1945. The following year it was decided to observe a Remembrance Day for both World Wars, to be held annually on the Sunday before Nov 11, unless either Nov 11 or 12 was itself a Sunday.