I asked this question before and Kreig came back with a great answer from Larry.
I don’t have the quote, but it was pretty much saying that time in this game (not in global 40 exclusively) is like a rubber band where its stretched in some points and shorter in others.
Where some battles might be able to fit some sort of time frame, movement of units don’t fit. Using six months as a base means that it takes ships over a year to get from the US to the action in the Pacific. Planes could have flown around the world a couple times, let alone made the flight from the US to Russia, in six months.
It’s nice to be able to do because most of us that play the game also know a lot about the the battles, but it’s more feasible to say I think D-day is possible because you notice an anglo-american armada forming than it is to say because it’s round 9.
If I had to make my own personal guess I would probably say four months, going on a mix of how long the games lasts and what the other posters have said about it supposed to being three months.
At 12-13 turns (at turns of 3 or 4 months each) that makes it 1944 when the game ends, and historically you can Hitler really had no shot of fending off Russia once the west landed in Normandy. He probably didn’t anyway, but the war was over once Overlord was succesful. If you wanted to go the extra four or so rounds to make it summer of 1945 the axis would be in complete shambles by then.