Any dates that are highlighted (with links) have an event(s) on that date and are viewable by clicking on that date.

From your personal calendar section, you can add a PlaneQuest global event (but it must be approved by the PlaneQuest admin), create a new club calendar, create an event for any club calendar that you are a member of (providing you know the club password), and add yourself to a club (providing you know the club password).