Trivia

In military parlance, D-Day is a term often used to denote the day on which a combat attack or operation is to be initiated. The terms D-day and H-hour are used for the day and hour on which a combat attack or operation is to be initiated. They designate the day and hour of the operation when the day and hour have not yet been determined, or where secrecy is essential. The letters are derived from the words for which they stand, "D" for the day of the invasion and "H" for the hour operations actually begin. There is but one D-day and one H-hour for all units participating in a given operation. It is unnecessary to state that H-hour is on D-day.

D-day for the invasion of Normandy was set for June 6, 1944, and that date has been popularly referred to by the short title "D-day."