A decade ago, the end of World War II was 54 years in the past. Right now, the end of World War II is 64 years in the past. If A-theory is true, these are genuine properties of WWII, and it has changed in respect of them. But something in the past cannot change. So A-theory is false.
The A-theorist's best answer to this argument is, I think, that this is a mere Cambridge change. A mere Cambridge change is when an object does not change in respect of intrinsic properties, but something else around it changes, which makes appropriate the application of a different predicate to it. The classic example is that x may grow shorter than y without changing in height—simply because y grew taller. The change in x was Cambridge and that in y was real.
A mere Cambridge of an object x change requires something else, a y, that really changes, where x's change consists in x having a description that makes reference to x's unchanged and y's changed qualities. Let us try to see how to do this for WWII.
Option 1: WWII has the unchanging property of ending in 1945. But 1945 has a changing property—it once was future, then was present, then was past, eventually being 54 years in the past, and now being 64 years in the past. So WWII, or WWII's end, undergoes a Cambridge change in virtue of 1945 (or a specific date in 1945) undergoing a real change. But the idea that 1945 should undergo a real change is at least a bit problematic, I think. It is plausible to say that 1945 is in the past, and so it shouldn't be able to really change. The alternative seems to be to makes times be something abstract—but the idea of abstract entities really changing is also troubling. So one would need to make 1945 be an enduring concrete entity. That's weird.
Option 2: WWII has the unchanging property of ending, say, 15,000,001,945 years after the beginning of the universe, but the universe has a changing age. When we say that WWII ended n years ago, we mean that the year that WWII ended, say 15,000,001,945 cosmic era, is equal to the age of the universe minus n. So, the end of WWII doesn't change, but the age of the universe does. This seems to work, but leads to further puzzles. What kind of an enduring entity is the universe? What is this property of age that so inexorably grows?
Option 3: WWII has the unchanging property of ending in 1945, but there is an objectively changing fact—the fact of which time is present. And in virtue of the latter changing fact, which does not consist in a change in any entity, 1945 undergoes Cambridge change. This view requires a relaxation of the account of Cambridge change—it doesn't require entities to change. (One might try to say that propositions reporting what time is present change in truth value. But that had better be true in virtue of something else.) I think the idea of change that does not happen in virtue of anything's changing is dubious.