If someone's giving you shit over it and you need a conversational out, remember that there are five categories of christmas movie:
- the Rankin-Bass (and its subcategories like the Peanuts)
- the DieHard
- the Hallmark
- the Biblical
- and the Tradition (not "traditional")
The Rankin-Bass is a christmas movie about Christmas Lore and Christmas Things specifically. Usually animated, almost always whimsical, tells Meaningful Stories through absurdist humor and/or charming childishness. Expect just-because non-sequitur moments galore.
The main schools are the classic Rankin-Bass, where they just keep inventing Christmas Lore like the Heat Miser and the Island of Misfit Toys and the fact that Bumbles bounce and the elf craves the dentistry, and the Peanuts, where aside from a dancing dog it's pretty normal.
The DieHard, also known as the Home Alone, is a movie that could take place at any time of year, but chooses to leverage christmas for convenience, symbolism, and/or added american nuclear family emotional impact. It's not about christmas, but christmas is important to the work.
The Hallmark is similarly not actually "about" "christmas", but gets special categorization separate from the DieHard because it's very specifically about the people involved and/or their relationship as a central focus to the movie, and even more about the feels.
The Biblical is basically just "hey you remember the baby jesus story? Yeah let's tell that, only without the vampires". Sometimes they get creative with it, sometimes they don't. Not much to say about this category.
Finally the "tradition" category is a catch-all: these movies don't actually need to have anything to do with christmas, winter, or the holidays at all, but because a family or group watches them regularly (such as the Lord of the Rings trilogy) they've become Christmas Movies.
Interstitial movies also exist, like "It's A Wonderful Life" and its predecessor "A Christmas Carol", both of which could theoretically take place around any other initiating moment, meaning that the events are due more to seasonal depression than seasonal dependence and so they exist somewhere between the Peanuts, the Rankin-Bass (christmas angels and ghosts etc) and the Hallmark (very much about the Feelings), or A Christmas Story, which is somewhere between a Home-Alone and a Hallmark, and so on.
So there you go, if your pushy uncle or edgy younger brother won't stop ragging you about how you don't get it, Die Hard is totally a christmas movie because (with the requisite smug grin and shit-stirring tone), you've got scientific categorization to volley back.