I once read a short story where the punchline was that the "christmas season" started on June 1 and ended on Dec 25, and only a few people remembered that christmas was a single day at all. I wish I could find it. I think it was in a collection of speculative fiction stories. Another detail is that most people didn't know that christmas songs had origins; they were all assumed to be trademarked jingles of different brands who had modified them.
More details: The main characters are a male, who works in marketing, and a female from an old fashioned family. The male is the one who only recognizes the "modern" christmas season, while the female is confused by his society. The female's father is very upset at the male's lack of knowledge or respect for the holiday.