A different kind of calendar!
These are chocolate Advent Calendars. Counting down the days till Christmas with Sonic is even more fun when you add chocolate candy to the process. These are for 2 different years & each features a snow scene with Sonic. The first has him on his snowboard doing a trick, and the second has him dressed in a mini Santa outfit in front of a tree with balloons.

The little doors are numbered, one to open for each day to see which chocolate you'll get. The doors can be shut again so you can see the whole scene. What's that black rectangle in the corner? It is a "FairTrade" seal, to ensure that no slaves were used to gather the chocolate. (Yes that is an actual consideration to have to take in the 2010s era when these were made) These were likely a Japan only item.