Before doing any troubleshooting I would recommend backing up your data (http://support.apple.com/kb/HT1553 for the computer and http://support.apple.com/kb/HT1766 for the iPhone). Calendars and contacts tend to be important to people and are complex in nature which increases the chances of mishaps.
Make sure you have installed all software updates on your Mac from Apple by going to Apple > Software Update.
Update your iPhone too: http://support.apple.com/kb/HT4623
Make sure you have turned on Calendar syncing in iTunes for your iPhone: http://support.apple.com/kb/HT1296
Turn your iPhone and your computer off and back on and try again.
If your calendars still don't sync from the iPhone, reset your computer's sync services: http://support.apple.com/kb/TS2481
Hope that helps.
I have this same problem. The interesting thing is this. I can add an event on my iPhone. Sync using iTunes. Then I can add an event on my iPad. and sync it also. All events will show up on both my iPhone and iPad (meaning, the event I just added to my iPad will show up on my iPhone and vice versa), but neither show up on my Mac iCal.
I found this article (http://iphonewriter.blogspot.co.nz/2008/05/how-to-fixing-ical-iphone-sync-issues .html) which solved the problem for me after much hair pulling.... "Here's the down and dirty fix:
- Open iCal and backup or export your entries. Make a note of the fie name and location, you're going to need them in a minute. Once your backup/export is completed, close the iCal application.
- Open Finder and remove everything inside the "Username/Library/Calendars" folder. For instance, if your username is "Joe", then move everything inside the "Joe/Library/Calendars" folder.
- Open the iSync application. It's located in the "/Applications/" folder. Once iSync is opened, go into the iSync Preferences (iSync -> Preferences) and push/click the "Reset Sync History" button. Then, close the iSync application.
- Re-Open the iCal application and Import (File -> Import) a new calendar. When prompted, use your notes from Step #1 to select the file your created earlier. Once completed, close the iCal application (you should have all of your calendar entries back.)
- Open the iTunes application and connect your Apple iPhone to the computer.
- 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.
- Click the Apple/Sync button. New, modified and deleted entries should now be syncing correctly.
That's it! You should be all set and iTunes, iCal and our Apple iPhone should all be playing nicely as friends again. We've used the exact method to repair our own Apple iPhone at least once... maybe even twice."
My iCal was actually fixed without re-importing my old backed up iCal entries as per step 4....which was a pleasant surprise. Hope this helps somebody!