How many days was operation overlord?

Answer 1

Operation Overlord was merely the plan to make a successful landing, to gain a toehold in Europe. It was done in a single day. But the planners had planned ahead to D+90, that is, 90 days after the landings. They did not try to go any past 90 days because they were certain that events would intervene and their plans would only be approximated anyway, and the longer past the initial landings, the more actual events would cause deviation from their plans. By D+90 the planners estimated the Allies would be closed up to the Seine River, which was roughly accurate.

It took about seven weeks after the initial landings for the Allies to build sufficient strength to break out of the beachhead. The Germans had most of their strength in the cordon they threw around the landed troops, trying to contain the invaders, and once the Allies broke through this crust, there was little to stop them going where ever they wished in France, except for their own shortages of gasoline, ammunition and supplies.