Doesn't make it a Christmas Movie though. The movie itself has nothing to really do with Christmas, it only takes place on Christmas Eve. Heist could have been done during any holiday where the office was closed.
I don't know why some people have such stringent requirements on what is or is not a Christmas movie, but only when it comes to Die Hard. Does there need to be elves to qualify? Reindeer?
Home Alone is almost universally considered a Christmas movie, yet a kid could be left at home to deal with robbers any other time of year. Bad Santa is considered a Christmas movie but has no Christmas theme outside of the occupation of the main characters. I'd even argue that A Christmas Story could be centered around Ralphy's birthday and it wouldn't change the plot. It would only mean AMC wouldn't play it on repeat for 2 weeks leading up to Christmas.