If KaleunMarco remember his noodlings with the flotillas in OM/Dark Waters, and the game will indeed go to December 31, 1999 - YEAR 2000!!! Look-out, the world as we know it will come to an end that day, because a computer can't run beyond that!!!
I am reasonably certain you can go beyond the end of WWII - not 100% though... ETR3(SS) or jhapprich (among others) could probably tell you for certain. I do not recall the "trigger" for the end of the Stock game sequence. But it is a bit of a bother to find all of the limiting date factors, and to make all of the "messaging" and other aspects of the game conform. iambecomelife has spent a good deal of his time in Wolves of the Kaiser doing 3D modeling, but I'm sure he has spent a considerable amount of time on the "date" issue also.