We arrived on 11/6 and Main Street was all decorated with the big tree, wreaths, and garland. It was so beautiful!
On 11/9, I saw them setting up the ginger bread display at the contemporary and then when we went to MK that day, the castle was all decorated. On our last day, 11/12, they were projecting lights on the castle. At one point it looked like it was all frozen and then another time it looked like a candy cane.
When we left on 11/13, our hotel (AKL) was not decorated and I do not remember seeing decorations in the other 3 parks during that week.