You have a calendar entry, or two or three. I recently ran into this same exact issue and, with the help from Sampson Apple, we worked thru the issue to resolve. Now, if you have iCloud control panel set up on your PC/Mac, you should have no problem syncing both ways, but in this case, my boss didn't do his homework on iCloud and the Outlook syncing process. My boss hadn't finished the process of creating his own 'iCloud', therefore his iPhone wasn't able to send 'iCloud' events to Outlook, because his PC had no clue what to do with iCloud, since the Control Panel wasn't installed. So, in final, make sure that with the iPhone 4/4S (iOS5) that you have iCloud set up TOTALLY. All of the sudden, the events were all syncing both ways. So, I went into his iPhone, changed the home/work(green/purple color) back to 'PC events (blue).

The events that he created on the iPhone were 'iCloud home/work' calendar events, as opposed to 'PC Calendar events'.

He created an iCloud account, and set up his calendars to sync through iCloud, but did not install the iCloud Control Panel for Windows (yet).

Certain events were syncing back and forth, but others weren't.

We were having issues getting his calendar items to sync back and forth, as he used his iPhone on the road/at home, and the Outlook '03 in the office. My boss got a new iPhone 4 and uses Outlook '03. Maybe this will help someone having some issues syncing 'both ways' with outlook/iphone calendars. Simply go to iTunes on your PC and 'Sync' once again. Select 'Done' x2 to return to Event Details Under 'Calendar' select 'Calendar' 'From My PC' To Modify in 'List' view:- Tap on appointment

Any appointments that don't have the blue dot will need to be modified, as basically only those with blue dot will sync to Outlook 2007.

Now go back to your iPod calendar and select 'List' view. Select - 'Calendar' under 'From My PC' heading (Blue dot) Verify 'Calendar' is selected in Outlook 2007 under 'My Calendars'. Reason for discrepancies, was my default Calender on iPod, was set to a different Calendar than Outlook. As iPod Touch has same functionality as iPhone 4, I'm guessing the same resolution would work for iPhone also. My iPod Touch was syncing with calendar entries from Outlook 2007, but Outlook 2007 wasn't syncing with appointments entered on my iPod calender.

I'll share simple solution that worked for me.

Itunes calendar sync with outlook 2013