Each adventure is a separate one-session one-shot. If you want a campaign, you will want to develop your own story to tie the adventures into a campaign, and will probably need to add a few more adventures so the players gain enough experience. The lowest adventure is for levels 1-3 and the highest is 7-9, so you could run a party from 3rd to 7th level with the calendar adventures, as well as Loke's "RPG Toolkit" adventures.