Remembrance Day (sometimes known informally as Poppy Day owing to the tradition of the remembrance poppy) is a memorial day observed in Commonwealth member states since the end of the First World War to remember the members of their armed forces who have died in the line of duty. Following a tradition inaugurated by King George V in 1919, the day is also marked by war remembrances in many non-Commonwealth countries. Remembrance Day is observed on 11 November in most countries to recall the end of hostilities of World War I on that date in 1918.

The tradition of Remembrance Day evolved out of Armistice Day. The initial Armistice Day was observed at Buckingham Palace, commencing with King George V hosting a "Banquet in Honour of the President of the French Republic" during the evening hours of 10 November 1919. The first official Armistice Day was subsequently held on the grounds of Buckingham Palace the following morning. During World War II, many countries changed the name of the holiday. Member states of the Commonwealth of Nations adopted Remembrance Day, while the US chose Veterans Day.

From Wikipedia