Although D-Day has become synonymous with the Allied landing on June 6, 1944, in Normandy, it was used many times before and since.
The D in D-Day simply stands for “day,” just as the H in H-Hour stands for “hour.”
Both are commonly used codes for the fixed time when a military operation is scheduled to begin.
“D minus thirty” means thirty days before a target date while “D plus fifteen” means fifteen days after.
