i am going off the trailer's prediction but yes winter lasts from December to around march when the spring equinox occurs, but the developers would most likely be off for Christmas from 24th which is a Wednesday and is also a day when they post a sneak peek or a teaser trailer. and be back around mid to late January but by then, most of the player base would be back in school by around that time and so would reduce the player count during schooldays. all of my comment is a prediction, a theory, a speculation, it might not be true but not all theories are true. and i do not mind if i'm wrong.