The reason I'm writing about this today rather than tomorrow is that as soon as I'm done, I'll be sad. It's difficult to part with a story, it really is. I live in the world I write about; it's my home. And I will feel sad when the day after tomorrow arrives, and I will no longer be working on Xmas Carol.
That's why I'm announcing the "happy" news today. By 5 pm tomorrow, you can shout it from the rafters: Xmas Carol is done!