Overview: Christmas in Stockholm 2016
Advent, leading up to the holiday itself. This is the time when you can visit Christmas markets, see holiday concerts and eat the traditional Christmas smorgasbord (julbord) at restaurants. This basically all stops after December 23rd. There are no holiday markets open on the 24th and 25th and only a couple of restaurants that still serve julbord.
museums & sightseeing tours and department stores & shopping centers to get a good idea. I will also write a post in the middle of November about the different Christmas markets in Stockholm.