Heimskringla lists three blóts that all were obliged to attend: the first was at Winter Nights (at vetrnóttum) and for fertility of farm and field in the coming year (til árs). Winter Nights signifies the start of the winter half of the year; it is sometimes fixed at October 14, but Icelandic tradition places it on the Saturday between October 11 and October 17.
Bede says that the heathen Anglo-Saxons called October Winterfylleþ, which he explains as meaning “full-moon of winter” because it began the winter season; however, other Anglo-Saxon sources state that winter began on November 1. The Anglo-Saxon months were actually lunar, and the calendar reform has shifted our dates; Winterfylleþ starts on the new moon in October. Also, winter comes appreciably later in England than Iceland. Thus, it is quite reasonable that the same festival was observed up to three weeks later in the warmer climate.
Also, the Heimskringla account may be combining two holy tides; at any event, modern heathens do celebrate two different fall holy tides. Winterfinding, which has little historical justification, is our harvest thanksgiving. Winter Nights/Winterfylleþ is more usually celebrated as a day to remember the dead. In the Scandinavian lore we read of Dísablót (celebration of the dísir) and of Álfablót (celebration of the álfar, or elves). The Swedes evidently celebrated their dísir in early spring, because that is when Disting (which would have been Dísaþing in Old Norse—the Thing of the dísir) is held, and Bede says the first day of Yule was Módraneht, “Mothers’ Night.” Otherwise, so far as I can determine, none of the several references to blótar to the dísir and álfar gives the season. But modern tradition has it that the dísir are our foremothers and the álfar our forefathers, and perhaps under the influence of the Celtic Samhain and more recent Hallowe’en, and of the Mexican Day of the Dead, most modern Asatru celebrate our ancestors at Winter Nights in mid or late October, and many Anglo-Saxon heathens do the same at Winterfylleþ on October 31. For many of us, Hallowe’en may seem a logical date for such a celebration, and it also conforms to the fact that many of us live in relatively warm climates where winter truly sets in at the very end of October.
Winter is also the time when Ullr/Wulþor and Skaði/Scæðu are more evident, when many have hunting season and are mindful of them as patrons of the hunt and guardians of the forest and its denizens, and when the Wild Hunt rides—often with the dead riding along, and always bringing terror as well as wonder. It is not inappropriate to think on death at this time; winter is a harsh time of year. But it is also a time to feast; November was Blótmónaþ in the heathen Anglo-Saxon calendar because the animals killed were offered as well as preserved for winter provender. We feast earlier in the fall in thanks for and enjoyment of the harvest; we feast at this holy tide in preparation for winter.