I wonder why we say events happen "at Christmas" but "on Christmas Day"? (It's not unique to Yuletide, it's a constant: at a season, on a date. At Easter, on Good Friday. So on and so forth. The same events: they got married at Christmas, they got married on Christmas Eve. Like that. Why is it like that?)
This post brought to you by the fact that to other peoples, it's not like that. I can't get used to "on Christmas", it's like stubbing my toe every time.