funnily enough, super important christian stuff has happened on/near halloween. If I am correct, Martin Luther essentially started the Protestant Reformation on the 31st of October.
Another note: I live quite far south, and of course live among many christians. Thankfully, they just treat halloween as a fun day to get candy. Many churches around here put up a bunch of halloween games and festivities for everyone, costumed with kid-friendly spooking.