It strikes me that people of antiquity would have had lives strongly dictated by whether the sun was up or not. Sure in your home you could have a fire going on the hearth providing heat and light but where candles and lamps affordable enough before industrial revolution for common people to work outdoors during the night?
If you lived far north enough that your winter daylight hours where 3 or 4 if any would you simply have to do all your outdoors work during those hours?
The short answer is that generally speaking, one had to try to make the most out of the light whenever it was available. However, the annual rhythm was such that there wasn't that much outdoors work to be done during the darkest days of the year.
I'm not qualified to answer for the Vikings, but I believe some idea can be gained from the practices of later period. In the (about) 1500s-1800s Finland, the "agricultural year" traditionally ended on St. Michael's Day (29.9. in modern calendar). By that day all the harvest had been gathered, most of the livestock slaughtered, and the fields prepared for the next year.
Only some animals were saved over winter (due to difficulties feeding them) and in any event poorly fed cows etc. did not produce milk in wintertime. Nevertheless, there was a lot of work in feeding them; generally, this would keep the womanfolk very busy with at least five daily feedings and preparing the meals.
Men might go hunting, but most people would stay close to home and be engaged in various crafts: winter was the time to make things, summers would be so busy for farmers that there would be no time to make, say, new clothes or farm impediments unless absolutely necessary. These would be made indoors, in what little light there was to be had from the fireplace and burning wood splints in splint holders (that is, poor man's candles).
Outdoors work would be limited during winter, both because of lack of light and low temperatures. The most important outdoors work was probably logging: particularly timber for buildings had to be felled during wintertime. There would also be some hunting and fishing, and some preparatory work such as driving manure from cattle sheds to the fields.
Winter was also the time to gather together, sleep, and tell stories. There are some theories that bipolar personality disorder (manic depressive illness), for example, might in fact be an adaptation to northern rhythm of life: you almost hibernate during winter and are hyperactive during summer.
HOWEVER, it is clear that sometimes one simply had to work at night. The Moon was sometimes called "the tenant-farmer's Sun," and not just in jest.
Sources:
Vilkuna, K. (1950) Vuotuinen ajantieto. Otava, Helsinki.
Jalasmäki, K. (2004) Perinteinen karjatalous. University of Helsinki.