I have a shared calendar (shared with one single user). I want to (a) stop sharing it, and (b) delete it. Can't seem to do either. I've tried from both the iCloud side and from within Calendar app on Yosemite. I can change the sharing mode ("View & edit", or "View only"), or rename the calendar, but the delete option is never enabled. From the iCloud side, I cannot delete the calendar either, nor can I disable the sharing.