The winter period is from August 27, 2021, to May 27, 2022.
It is divided in two, the first from August 27 through Christmas, which can be booked as of August 16 at 8:15am. As of November 1, you can book for the new year, January 5 – May 27.
During the winter, houses can be booked both on weekends and for a week at a time, except through the holidays (Christmas, New Year’s and Easter), when only weekly rentals are available.
More info here.