The Advent Calendar is only operative in the Month of Celebrating, December. Every day of that month, a new Christmas-related animated video can be seen along with some prizes to go alongside of it. (They include Neopoints and items such as Toys, Food, Books, a Petpet, and Neocash items.) From 2012 to 2020, items were hidden in each day's animation and reward a wintery-themed bonus prize if discovered; from 2021 onward, the owner of the Advent Calendar, Reina, will pop up in beside each day's animation and reward you once she is clicked on.
The Advent Calendar Archives is where you can see all the animations that were showed during all the Calendars. All of the animations from 2000 through 2016, however, were produced using Adobe Flash. On Jellyneo, they are converted to a modern movie format so that you can continue to enjoy them each holiday season, even after Flash is gone.