What is the core criteria for a Christmas movie ??

The debate over whether "Die Hard" is a Christmas movie has been raging for decades, but it got me thinking -- what qualifies a film to be considered a "Christmas movie"? You could argue the obvious factors such as Santa Claus, talking reindeer or toy-making elves being characters, but that would rule out obvious Xmas flicks like "A Christmas Story" and "Home Alone".

Unless the movie already has Santa Claus in it, the single qualifying ingredient for a Christmas movie is one of the lead characters undergoing a Grinch-like transformation from a sourpuss to a loving, caring person -- with the holiday season as the backdrop of the film.

Therefore, "Die Hard" would not qualify as a Christmas movie. Santa does not appear as a character, and the two lead characters (Hans Gruber and John McClane) undergo no Grinch-like transformation of their characters. The movie takes place during the Xmas season, but that alone does not qualify it as a Xmas movie. Pretty much any movie that takes place in December could qualify as a Xmas movie if that alone was a criteria, and that doesn't make any sense.

My litmus test would probably qualify "Sound of Music" as a Christmas movie, although Santa Claus and holiday decorations are not seen in the movie, and it doesn't seem to take place in December so that could disqualify it? However, Captain von Trapp does undergo a transformation from an uptight, condescending douche to a loving father and husband by the end of the movie.