Good eye, @RyanLahti ! That small calendar populates the home page of a course when the instructor has chosen to use the Syllabus page as the course home page; the other home page choices do not display the calendar in the right sidebar but instead provide a View Calendar link that directs users to the same full page calendar that can be accessed from the global navigation.
I'm assuming you're a student, and if that's the case, you might want to let the instructor of the course without the calendar know more about how having it on the home page would enhance your course experience.
