Swedish food days have their origins in Christian traditions and the rules surrounding fasting. As in many other countries, the days leading up to a fast were a time for enjoying rich, fatty foods — a custom that gradually evolved into a broader culinary tradition. Over time, various Swedish foods and pastries earned their own dedicated days in the calendar, set aside for appreciation and celebration. Today, individuals, companies, and organizations continue to introduce new food-themed days, contributing to the vibrant array of culinary celebrations observed across Sweden.

December does not have a lot of food days because there is so much food connected to Christmas itself.
Here is a list of food days in December:

Monday, Dec. 1 – Glöggens dag / Mulled Wine Day
Tuesday, Dec. 9 – Pepparkakans dag / Gingerbread Cookie Day
Monday, Dec. 15 – International Tea Day
Thursday, Dec. 18 – Kakans dag / Cookie Day
Sunday, Dec. 21 – Skumtomtens dag / Marshmallow Santa Day