Hello, xmas event is available after about 41 in-game days in Free Mode (around every 17 days a special event is started, first is Halloween second is Xmas). At that time a notify will appear on day start and a totem like construction will appear near the player's home (inbetween nest and the yellow builder guy). Interact with it to get a portal nearby, then interact with the portal to go on the Xmas adventure.
Cheers,
~NK