I never did accept that BW placement. It's CLEARLY spring, which means the book is incorrect unless there is specific story evidence that would 100% place it in December.
I also never assumed everything but one thing is wrong. My stance is the book is likely correct on most things. But, as with all books, humans make mistakes and errors can happen. That is why revisions and updated editions exist, to correct mistakes.
To YOU the most concrete thing we have is when the book decided to place the scene. But if we watch the film itself and pay attention to on-screen evidence, it's obvious that it's not late fall/early winter since leaves don't go from dead to alive within a few days. That IS concrete evidence.