Guild Wars: Wintersday is December 19th through January 2nd
The humans of Tyria celebrate the ending of one year and beginning of another. During this time the deities of Tyria battle over whether Spring will come early or winter run late. There are a series of WIntersday quests in Guild Wars: Prophecies, Nightfall and Eye of the North. Guild Wars: Factions has its own holidays. Unfortuantlky Wintersday is no longer updated with new festval masks because Arenanet has most of its people supporting Guild Wars 2, instead you can get masks from past years. I'm almost caught up.

Guild Wars 2: Wintersday begins December 16th.
Originally a human holiday, Wintersday is now celebrated by other races for different reasons (now that there are other playable races than just human).

Star Wars: The Old Republic's Life Day Begins December 16th (after update 3.0.1 which will fix bugs in Shadow of Revan, and implement 3rd Anniversary Vendors on the fleet). I''ll update the link if a new entry is posted later. A wookie holiday adopted by other races as an excuse to party.

Thanks, Guybrush.

Thanks, Guybrush, lots of goodies to be gotten. Have fun

The Secret World Middle of December. Previous Christmas stories will return and there will be one new storyline: The Christmas Conspiracy. The conspiracy begins with an invitation to a showing of “The Magic Flute” at the Albion Theatre. From there you’ll find yourself drawn into a conspiracy that touches the lives of several famous historical figures and find yourself exploring catacombs untouched for hundreds of years as you race against time to stop the Phoenicians from stealing the very heart of Christmas itself.

Thanks, Jarkeld. Sounds fun!

They messsed up Wintersday. Two quests telling you to take part in Wintersday to get ice shards, 100 for one mask, 99 for another, but none of the other quests rewards shards, the wintersday gifts they do reward rarely give shards and in 3 hours I had one monster drop one chard. There used to be quests that rewarded shards but they're not there. Makes no sense.

Hopefully, they can patch that.

Its possible the missing quest givers will appear after the weekend. Which is bad next week is my busiest work week up until Christmas which we're closed on and then I took 3 days off to visit my sister out of town.

Yes, this is not a good time to play, for sure.