Yosemite iCar/Calendar: Deleted calendar account still shown in sidebar and iTunes

Hey everybody,

When I went back to iTunes Wi-Fi Sync to transfer my contacts and calendars to my iPhone, I noticed that calendars from my previous and now deleted CALDAV provider Fruux (fruux.com) were still on the list in iTunes. I deleted that account under System Preferences > Internet Accounts and checked again there as well as under Calendar > Accounts. The account isn’t mentioned anywhere there, so I presumed iTunes must have gotten the data from caches. It didn’t bother me too much at the time, so I ignored it.

For some reason, this old account suddenly reappeared on Calendar a few days ago. It doesn’t show individual calendars, but it shows the label in the sidebar. I checked under System Preferences > Internet Accounts again, but it isn’t mentioned. However, when I go to Calendar > Accounts, the account is suddenly there. I’ve tried to delete it from there, but the panel doesn’t respond. I unchecked “Enable this account” to remove the calendar from the sidebar, but the account is still mentioned on the list.

I’ve considered re-adding the account, but I have no access to it anymore (I deleted my account on fruux.com as well). I though that the Calendar app must simply be getting the data from caches, so I went on to my user library folder under Calendars and Preferences and deleted all entires relating to iCal/Calendar. I of course backed up my data before, manually as well as through Time Machine.

However, since then my Calendar app has gone crazy. Suddenly I can’t access my Facebook calendar anymore. I deleted it from Internet Accounts, but it is still shown under Calendar > Accounts. It also shows an old Yahoo! account which I don’t use for Calendar at all (only Mail), but it’s likewise shown in the sidebar now. And worse still: Fruux is still there. Deleting the cache has had no effect, Calendar was able to rebuild everything again. I’ve restored the Calendar folder again and am back to where I started.

Any ideas on how to completely reset Calendar? I would prefer to start from scratch at this point.