MobileMe: Resolving Duplicate Calendars in iCal with the MobileMe Calendar

Resolution

Confirm you are experiencing this specific issue by logging into me.com/calendar and see if your calendars are duplicated there. If they are not duplicated on the MobileMe website but they are in iCal, continue following the rest of this article. 

1. Initiate a sync

Choose Sync Now from the Sync icon in the Mac OS X menu bar.

Once this sync completes, your previous calendars in the On My Mac section of iCal should no longer appear.

2. Delete local calendars

If the duplicate data is still there, follow these steps: 

Note: It is recommended that you backup your data before doing this. See MobileMe: How to back up calendar data using MobileMe Calendar for instructions.

1. Under the On My Mac section in iCal, remove the checkmarks from the boxes next to all your calendars.
2. Examine iCal and make sure the events and To Dos that you expect to see there are still displayed.  If they are not, your data may not have been migrated successfully. If this is the case, setup your calendars again with the steps in this article.
3. Click one of your unchecked calendars to highlight it.
4. From the Edit menu, choose Delete.
5. Confirm that you want to delete the calendar.
6. Repeat for each calendar under the On My Mac section that was duplicated.

Note: Do not delete any subscribed or MobileMe calendars to resolve duplicates (such as the one shown in this example):

For more information about subscribed calendars, see this article.