I ended up with 2 complete iCloud collections of calendars somehow. Deleting one would delete both.
I don't know about the Addressbook issue but here is what I did for duplicate calendars.
The first thing I want to check is if the web-based iCloud on Safari is showing duplicates. If so, delete those. That is the "master" list and the other devices will follow when they sync.
If that is not the case I would Export a copy of the calendar(s) I want to save. This creates .ics files for importing later. For the Addressbook go to File>Export>Addressbook archive.
Delete once again your iCloud account from the Mac. Go to the web and delete any calendars that remain.
Import the backup .ics calendars. Restart iCloud from the System Preferences and turn on the calendar feature. You will have the option to Merge; select it.
Another thing may be to just wait a period of time before reinstalling things. There sometimes seems to be a lag between changes on the Mac and changes showing in iCloud. This delay can be a few minutes but perhaps waiting longer will be sure the syncing has happened.
This answer from another thread may work. Instead of deleting iCloud account, just uncheck and check the features in the iCloud System Preference Pane. Then select Merge when rechecking.
Thanks MaxGuru, but that absolutely did NOT do it. That was one of the first things I tried.
OK -- so, I have returend from a TWO HOUR Genius Bar appointment and here is what we figured out: there was NOTHING that could be fixed to prevent the duplicates, not matter which solutions we tired (all those mentioned in the forum, and elsewhere).
What did we do?....First, I have always backed everything up, so I had backups to play with. Make sure you back up everything before you try anything else I mention here (i.e. do an export for iCal, Address Book etc. -- I worked from fresh copies from my Time machine backup from Monday before all this mess started to assure it was as clean as possible.) I put those on my desktop for the time being so we can access them quickly and easily.
Step 1: delete all calendars, address book, reminders, notes from desktop, iPhone, iPad, and iCloud.com (yes, delete it all).
Step 2: put a clean copy of all that data back on your Mac (or PC) from your backup.
Step 3: In iCloud, turn off all calendars that they create that you are not using (work, home, calendar for example are calendars iCloud creates that I have never used since I have created my own and named them MyLastName, Holidays, etc).
Step 3: Turn iCloud off everywhere: on your iPHone, on your Mac, and on your iPad. Make sure you turn off every single feature, not just calendar. Totally turn everything off. LOG OUT OF ICLOUD.COM, DELETE iCloud account on your iPad, DELETE Icloud account on your iPhone.
Step 4: Restore your calendar, notes, address book on your Mac from backup (do not restore reminders - those are gone, never use old ones again, you'll create new down the road -- it just will not sync no matter what from an old copy at this point)
Step 4: Hard-wire sync your iPad and your Mac through iTunes. You'll have to turn on all the sync features. DO NOT sync your iPhone (unless it will be the only thing you sync with your iCloud and mac). Go back into the Info tab and after syncing turn off all the sync features you turned on (contacts, calendars, etc)
Step 5: Disconnect from iTunes
Step 6. Log back into iCloud.com on your Mac. Leave it be.
Step 6B - and this is important: On both your iPad and your iPhone, turn off all calendars that are not yours as per above.
Step 7. Log back into iCLoud on your iPad. Your iPAD will become your primary sync source. Now go ahead and one at a time turn on the address book (wait a bit, check icloud.com on your Mac to make sure it was connected properly). Then turn on the calendar (wait a bit -- depending on how big your calendar is, it might take 5-10 minutes for it to all upload to iCloud from the iPad). Check iCloud to make sure it is there. Same thing with all the other features -- one at a time from the iPad first.
Step 7. From your Mac, go to Preferences>iCloud> and turn on one feature at a time. It should now be okay without any duplicates being introduced. Give it a few minutes to make sure everything remains stable.
Step 8. Now connect your iPhone to iCloud-- be aware this might cause duplicates on your iPhone -- not to worry, there is a way to fix that. Add one feature at a time as you recreate your iCloud account on your iPhone. Start with Address, then then others...
Step 9. Check your iPhone calendar. You might have duplicates on your iPhone. That is okay. DO NOT do any further sync at this time. If you only have one copy of your calendars on your iPhone, you are good to go, and your iCloud connection should now be stable. Step 9B -- If you have duplicates on the iPhone, go to iCloud settings on your iPhone, and uncheck Calendars. When it says delete all on this iPhone, select yes. Wait a moment. Turn your iPhone back on. It should within a few moments push one single copy of the calendar to your iPhone. Now your are good to go.
Why this is such a hassle, is anybody's guess. We literally had two Geniuses at my local Apple Store working on this with me, and we had Apple's Tech Support on the phone the entire time through the process. When it takes about 7 people to correct a simple iCloud tech problem, you know there is something seriously amiss and there will be a lot of problems with people using iCloud for the smartphone features rather than the entertainment features down the road.
Anyway -- hopefull this might work for some of you. If not, good luck in finding your solution.
The overall answer seemed to have been to a) completely delete all old data and backup clean copies, and b) use the iPad DEVICE as your primary inital iCloud sync source. How backward is that, when your desktop/laptop should always be one's primary source.
No specific answer here but it would be interesting to know if you were syncing these devices with some other service before. I migrated from MobileMe to iCloud and was having duplicate entries in iCal, and I realized that it was syncing both MobileMe and iCloud. When I turned off MobileMe syncing, one set of data was removed and the iCloud data remained—exactly what I wanted. You mentioned that you were not a previous MobileMe subscriber, but it sounds like you are a savvy enough user to possibly have used some service to sync your calendar, address book, and whatnot (Google Apps? Outlook?). Maybe remnants from that service (or services) is what is at the root of the problem? Good luck!
Thanks for your thoughts, but no, that wasn't the case -- I am not a big believer in over-the-air syncing, and this whole iCloud mess was created when I tried doing that for the first time. As far as Google Apps, never! and microsoft products, not since 2001). I am generally a far-too-compulsive user about my data to do anything but manual sycs, so I thought I would give that a try.
The real thing here seems to be that Apple, again, doesn't take the business/power user into account when creating these things...of course it all makes sense now that we know what the problem was....why would I, or you, as an end user, ever even consider the importance of syncing notes, reminders, calendars etc, from a desktop when the real reason anyone would really want to use iCloud is to sync their music and be able to buy more instantly over the air from Apple to use on their iPhones/iPads...from their design point of view, it completely makes sense that the only way they make money is off of the music/movie sales, not us folks who actually want to use the equipment as a smart phone and control their data from a desktop.
It's why my company won't even allow people to use iPhones - still stuck in the BlackBerry ether, but it does what it is supposed to for productivity vs entertainment.
PS.....end of saga -- everything is back to the way it should be; duplicates are gone; and so is iCloud. I have turned it all off and it's going to stay off. Nothing but problems that I can forsee by leaving it on.
I've tried a number of syncing programs over at least 15 years and none were successful. Either they missed changes or made multiple copies of contacts and calendar events. iHub and iCloud being the most recent. There seems to be a fundamental problem with using a server whose purpose is to sync the data between self contained applications which reside completely on each device. The server can be embedded in one of the computers on your local network such as iHub and Chronosync or in the Cloud such a mobileme and iCloud.
The only solution to this that has worked in my experience is putting the applicaton on a web or cloud server which then makes our devices just an intelligent and pretty I/O device. In the days of a centrally located mainframe computer we would be considered "Dumb Terminals." Financial institutions still use this approach today.