Christmas at Disneyland is so magical. The big tree is up, snow falls on mainstreet, the castle and It's a Small World is decorated, and it starts in mid November. You can enjoy the magic of the season at Disneyland without having to go during the crazy weeks of Thanksgiving, Christmas, and New Years. They usually have the parks fully decked out by mid November. The weeks before Thanksgiving and the first two weeks of December between Thanksgiving and mid December are the best times to enjoy the parks which have lower attendance during these times. They will still be crowded but not as crowded during the really busy times.