https://www.gamespot.com/articles/pokemon-go-christmas-event-begins-today-adds-more-/1100-6455777/

Pokemon Go's second Christmas event is scheduled to begin very soon. Like last year's holiday event, it introduces new Pokemon to the popular mobile game, makes it easier to get your hands on Pokemon Eggs, and brings back a festive Pikachu for a limited time.

Beginning at 1 PM PT / 4 PM ET / 9 PM GMT today, December 21, Ice-type Pokemon will appear more frequently in Pokemon Go, and players will have another chance to encounter a Santa hat Pikachu for the duration of the event. Like last year, it can evolve into a Santa hat Raichu, and this time players have a chance to hatch a Santa hat Pichu, as well. Niantic is also adding an additional 20 Ice- and Water-type Pokemon originally from Ruby and Sapphire to the game, including Milotic, Sharpedo, Wailord, Walrein, Relicanth, and more.