I'm on a roll here, but figured I needn't fill up channluv's excellent thread completely with irrelevant info But I've been looking this stuff up, and it's fascinating, and I know there are TE'ers with various connections to Scandinavia who might want to read.

Time: the year was divided into 2 parts, winter - skammdegir, literally "shame-days", or short days, and summer - nottleysa, "nightless", the time of no dark. They used moon-months too, but weren't fussy about counting them in summer, because the moon could be hard to see in the light nights.
Blót/sacrifice: the autumn or harvest blót was held on the first day of winter, for the fertility god Frøy. The harvest was then safely in. One wished winter welcome (!) and sacrificed for a good year.
The midwinter blót was not necessarily at the solstice when the days were shortest, but when the animals were at their fattest and the autumn chores were done. Maybe they just didn't have much to do Beer/mead was important ritually, it could not be stored for long. Some of the oldest laws specify that each farmer has to brew a certain amount of beer or mead within a certain date, or pay a hefty fine, and drink it with at least 2 neighbours. There was also a specific law governing the beer, blessed on christmas eve, that a farmer and his wife were obliged to brew and drink together. These laws are post-Christianity, but probably relics of fertility and harvest rituals for the old norse gods.
The midwinter alveblót was a private affair, one of the kings storytellers tells in a saga that he was travelling but was not allowed in anywhere because it was Christmas: "Do not come in, poor fool! said the crone, here we are all heathens, afraid of Odins wrath. Out! said the nasty old woman, like a wolf she chased me to the forest, said in the house they were holding alveblót".