The New Year Celebration is an Event that takes place Late Winter, 29-31 (in-game time). During this time the events area (behind the Hub spawn) changes and the Baker NPC appears along with some cake.
You can claim one New Year Cake from the Baker in the duration of the event.
After claiming your New Year Cake, you can right-click the Baker again and a New Year Cake Bag can be purchased from the Baker for 250k coins, which can hold up to 54 of your New Year Cakes and gives +1 Health for every unique Cake stored inside.
You can find out when the next event will be (real-world time) using this fansite.
If a person were to, starting with no previous cakes, collect a new cake every event without fail, they could fill the cake bag in 279 days (slightly under 40 weeks, about 76% of a year)
Due to an error for the 1st year, you could switch lobbies and get multiple cakes, some players collected over 100 cakes this way.
During the 69th New Year Celebration, SkyBlock went under maintenance for the v0.7.9 update, closing the game to 1Default ranks and preventing them from obtaining the New Year Cake. This closure was lifted shortly after the maintenance announcement and placed again after the event ended.
During the 71st New Year Celebration, players were given the 0th New Year Cake instead of the 71st New Year Cake. This was possibly a glitch from the 2020 anniversary.
This is the only event that was not cancelled by Dante when he was Mayor.
During SkyBlock Year 144-146 (from June 23 to July 4, 2021), the Baking Specialist appeared at -12, 70, -44 and handed out the Year 143 New Year Cake, because Hypixel was in maintenance mode during the New Year Celebration of Year 143. During the New Year Celebration of Year 144 and 145, both the Baker and Baking Specialist appeared.