I don't get this trope.
It's basically Meaningful Date as applied to horror films; the page seems to assert this is always the case in horror, but it's clearly not. Also, most of the examples lack any context, and the Buffy one is not an example of this trope.
So yeah, this needs work. I think we already have this by a different name, perhaps we could merge them?
Because monsters in Buffy don't pick any particular day to strike, but strike all year long. In one particular episode, some characters state that monsters won't go out on Halloween, but by the end of the episode they've been proven wrong about that. Buffy monsters do go out on every day, including simple tuesday and including halloween.
What? Another rename crowner? We got rid of the last rename crowner because, aside from the OP, no one had even talked about renaming the trope. That hasn't changed. This trope might have problems, but just doing a rename crowner without discussing it or thinking up alternatives names is not going to help anything.
Agreed, Meaningful Date is a trope.
Just to see if we're on the same page, the laconic of Meaningful Date would be: "A date that has has plot significance."
The title maybe would not be good.
It could be confused with date meaning "meeting".
In a quest to erase natter from the face of earth.
I would say "Important plot events tend to happen on important calendar dates."
It's saying that you're more likely to have an important story event (or the entire story) happen on Christmas, 4th of July, Guy Fawkes Day, or Lammas Night than you are on April 3rd.
The thing is, I don't think the date is necessarily meaningful in this case. I'm thinking of something like My Bloody Valentine, where the fact that it's Valentine's Day in particular has no special relevance or thematic significance. (That is, Bad Stuff happens on that day, but not because of anything special about valentines or romance or the martyrdom of saints.)
Horror Doesn't Settle For Simple Tuesday seems like a good rename to me, too.
(P.S. Don't we have an Arc Date or Recurring Date trope or something like that?)