I've seen discussions about when it is that the Christmas season officially starts and ends, and for the Scalzi household, it starts after dessert on Thanksgiving, and ends on Epiphany (which is Jan 6), although as a practical matter it ends whenever Krissy decides it's time to put away decorations, so, usually that means Jan 2nd or so.
@scalzi My sister and her family begin the Christmas season immediately after dessert on Thanksgiving by watching Elf together. We have adopted this tradition in my home with no regrets!