What is the significant about setting the story in December and during christmas

One could make the argument that as Phoenix makes the trip to take care of her grandson, she is sacrificing everything for him. She is the one who holds her family together. She makes the trip regularly and sacrifices whatever she must to take care of that family. Everything is against her - her race, society's prejudice, other people with whom (like the hunter) she has dealt all her life. Hers is a yearly trek and she goes as she always has.