Sometimes it can be helpful to separate long term project assignments from the general class schedule. For example, if there is an end-of-year research paper and presentation, it might be helpful to have a separate 'Research project calendar' that has all the due dates and milestones for the project. Then the project calendar can be viewed on its own and is easy to find the information, instead of perhaps getting lost in all the events scheduled in the class calendar.

Another example of a way you could use a special project calendar is when working on a group project. Group members can collaborate and share a calendar together so everyone can have access to the project meeting times, project deadlines/milestones, and other project related activities (going out to do a survey/market research, conducting an interview, etc).