From the first time I played the MB Classic A&A back in 1989, I have tried to figure out exactly what a unit or a turn represent in the real war. My best answer so far is that the Designer is correct when he says A&A is supposed to be a balanced and playable game set in the age of WWII, and with abstract units and timeline. Bit since a real A&A player never quits, this is my take.
The timeline in Global 1940 is intriguing, it may look like the first Turn represent a year of political actions, the next is 8 months, then 6 months, 3 months and after 20 Turns I would say a Turn equal a week. So it start slow and speed up on the political part of the game.
When it comes to land combat, and land units operational level in campaigns, I figure a Turn in the European map is like 2, 3 or 4 months. That was the time it took to capture a territory that size in the real war. I would prefer a Turn to be 3 months, because then we can cut the year into winter, spring, summer and fall seasons, the 4 distinct campaign seasons that was in the real war. I would also take into consideration that Napoleons Army, that walked on feet, combat moved from Poland to Moscow in less than 3 months. That was faster than German Tanks and Blitzkrieg 100 years later.
But then we have the non combat move, which in A&A is total bedlam. A Tank dont need 6 months to drive a few miles in peacetime. Put the men on a train, and they will be anywhere on the map during a Turn. When the real Germans were a few miles away from Moscow, Stalin moved half a million men from Far East to Moscow on train and it only took some days. On the A&A map, if a Turn represent 8 or 6 months, the Russian infantry in Far East would need many years to drive to Moscow, its like turtles would outrun them.
Then we have naval movement, and this is funny. A US ship unit take two turns from US to UK, a trip that would take from 5 to 14 days in the real war depending what kind of ship it was. A Cruiser at 30 knops would use 5 days and a Tranny at 15 kops would use like 14 days, and a Submarine at 9 knops a few days more. Now, if the first Turn is like 8 months, then an A&A naval unit sailing from US to UK would still be at open sea in the middle of the Atlantic, its like a raft would sail faster. I read in the news some years ago about a madman that crossed the Atlantic in a bath tube, and he was still pretty much faster than an A&A naval unit. So basically its pretty obvious that so far the naval part of an A&A game is concerned, a Turn is like one week or less. Another fun fact about A&A is that bridging units from UK to Normandy takes as long time as sailing that unit from UK to Canada. In the real war, a Tranny would use like 4 hours to cross the channel and dump some men at the beach in Normandy. This same Tranny would use 14 days to cross the Atlantic. Obviously its something derogatory about the A&A OOB movement rules. But, try to fix it with house rules, and balance get offset and the game broken.
The A&A aircraft range is funny too. The A&A fighter can fly from UK, cross Axis Europe and sink Italian ships in the Med. All in one move and without refueling in the air. In the real war a fighter could barely cross the channel in one move. But a long range Bomber could cross the globe in a move, but in A&A it got slightly longer range than a fighter. I figure a Turn would be like one day when it comes to aircrafts.