This is what I've never understood. The end of December isn't bleak. And it's not mid-winter -- it's only been winter for a few days.
Bleak mid-winter is the end of January, the start of February. That's when it's bad. That's when it's coldest. That's when people get depressed.
In the snowy northern parts of the world, I've often wished Christmas could be then, to help with people's moods.
Having it at the very start of winter feels like you're wasting all the cheer before we've gotten to the actual bleak mid-winter when you really need it!