You have one overall calendar with events from all projects and you can filter this to display a project-based calendar.
You can create anything you would like to track in a calendar. This could be an activity with a start and end date, an actual event like a shooting day or a milestone. Milestones can be marked as completed and will be displayed in your projects as well.
Besides a start and end date, you can add a description, tasks, file attachments and comments to an event.
Any WhoCan event can be displayed in your Google Calendar. After connecting your Google account, you'll see a new calendar called WhoCan in your Google Calendar sidebar.