i Cloud calendar, it is possible that syncing no longer works for that entire calendar.
I experienced this while I was traveling in late September 2012 -- the missing appointments were my itinerary which was in a calendar I share with my executive assistant.
Visit Stack Exchange When I create or update a calendar event on one device, it is not being propagated to my other devices via i Cloud despite having i Cloud enabled for calendars on all my devices and the Apple ID being the same everywhere.
Problem: Synching a shared calendar did not work from my Mac to i Phone (using i Cloud), but worked from i Phone to Mac.
In this case, it might be possible to change the calendar view in Outlook to a list view and drag-and-drop the appointments from the broken calendar to the new, working shared calendar.