Maybe try the instructions posted here :
It's in the seventh post down submitted by rorygilmore.
I've just fixed my iPad/iCal/iMac sync problems using his instructions.
Worth a go!
Thanks for the tip. Step 6 says:
"Within the Advanced section of the Info tab for the Apple iPhone, check the box the overwrites/replaces the Calendar data on the Apple iPhone."
But I would prefer not to completely override my iPhone calendars by my desktop calendars, since I have several newer entries in the iPhone calendars. Is there a way to avoid this?
As far as I understand the sequence, there's no way to avoid overwriting your iPhone calendars, but I'm sure someone will put me right if I'm wrong.
Synchronising means causing something to occur or operate in unison. Therefore the whole point of "sync" is for your calendars to share their data so that they hold the same information. If you want your phone calendars to differ from those on your desktop then perhaps "sync" isn't what you need!
I certainly want the two calendars to be in unison. But sometimes I update the calendars on my phone, sometimes on my computer. That was all getting sorted out nicely via sync--it seems that it automatically implemented the most recent changes on both calendars, regardless of which device the change was entered on. And wherever there was a question of which calendar to follow, it presented me with a choice. This is my understanding of how sync should work.
Sorry I misunderstood you.
So, on the basis that you do want your calendars to sync...
First off, I think in order to fix the sync problems you've been having, you'll have to carry out the complete replacement of calendar information on your iPhone with data from your desktop.
For any unsynced entries in your phone, I'd suggest you note them down then enter them into your desktop calendars before overwriting. Alternatively, you could do your overwrite then re-enter them into your phone afterwards. Hopefully on your next sync they'll appear in your desktop calendars.
I don't know how many entries you have (hope not too many) but I can't see any other way around it.
I finally got around to trying this, and nope, didn't work. Which is to say, the syncing process is still unpredictable. After resetting the sync history and restoring the old calendars, I tested the syncing process in two ways. On my iPhone, I added a new event, and I deleted all future occurences of a weekly event. After syncing with my iMac, the new event showed up on the iMac, but the recurring event continued to recur past its end date.
This is really ridiculous. Does anyone have any further ideas of how I can fix this? And why does Apple have such an obvious, shoddy bug in such a popular product? Is it fixed in newer versions of iCal? (I've been avoiding iPhone OS 6 because I hear that the new Maps app is bad.)