Some iOS 5 users have been using Contact and Calendar as yahoo Sync service, but now want to switch to icloud calender. I am also go to use my iCloud account as the default calendar account, instead of yahoo. Here is the tips for that.
How to move yahoo calendars to iCloud
* Export the Yahoo calendar to a .ics file.
* Create a new calendar on iCloud.com and import the file into it.
* You can also do this on iPad/iPhone device. First set icloud as the default calendar. Email .ics file as The attachment, open it, click an option to “Add All”, and choose iCloud calendar to add to. But the events seem not to be added to the calendar.