You can create additional personal calendars below My calendar.
How to create a new personal calendar:
In the folder tree, click on Add new calendar. A menu opens.
Click the Personal calendar menu item.
A window opens.
Enter a name. In case the new calendar should be a public calendar, enable Add as public calendar. Click on Add.
Also see
Subscribing to public calendars
Subscribing to Google calendars
Subscribing to iCal calendars
Importing calendars from files
Parent topic: Adding Calendars