Everyone loves a Steam sale, as there are countless bargains on offer on a range of games, and according to a source on NeoGAF, along with the suitable title of 'Prepare yourselves, the Steam Winter Seal comes Dec. 22nd', the Winter Sale will run from December 22 at 9:50AM PT (5:50PM GMT) to January 2 at 10:10AM PT (6:10PM GMT).
There's no concrete evidence to suggest this is true, so don't take this as gospel, but it seems feasible considering the dates, and the user, Tizoc, has predicted sales dates before. Not only that, but it started on this date last year too. What would you like to be discounted in the Winter Sale?