This one was a pain to figure out, so I am sharing it here in case others can use the info (or for the next time I need it myself).
iPhone supports syncing with multiple calendars, and displays them in a single integrated calendar using a different color for each. But have you ever tried to remove one of the calendars? There is no option to do so! And unchecking the calendar in iTunes simply prevents it from being synced in the future, but does not remove the unwanted calendar from the iPhone - all that left over data just sits there.
In my case I have an Exchange calendar and a local Outlook calendar on the iPhone, and I wanted to remove the local calendar and leave only the Exchange calendar. Here are the steps that worked for me (adapt them as needed):
- On the iPhone, go to settings, select the Exchange mail/calendar, and turn OFF Exchange calendar use.
- iPhone will ask you if you want to delete the Exchange calendar data, confirm the deletion.
- Then turn ON the Exchange calendar.
- iPhone will ask you what you want to do with the existing (non-Exchange) calendar data, giving you the option of deleting it.
- Go ahead with the deletion.
- As soon as Exchange syncs you'll have just that one calendar.
Pretty simple (although there really should just be a simple delete option!).