The server responded with an error.
I tried to delete a calendar and this error message keeps comming up.
I have the answer once and for all for this really annoying problem
1. go to iCloud.com
2. enter you apple id and password
3. click calanders
4. at the bottom of the left hand side of the screen is an edit button... click it.
5. press the red thingy next to the calendar you want to delete.
6. hey presto you calendar is finally gone
Hope this helps
Retrieving data ...