My boss has an iPhone 6s Plus + iPad Pro + Win10 PC with Outlook 2007. He set the devices so each has their own default calendar, but all calendars are set to sync in iTunes. He refuses to utilize any cloud services for calendar sync, and use iTunes exclusively to sync everything.
However, some events on iPhone were not synced to PC. Some events that can be seen on PC were not seen on iPad. Months of events go missing on iPad despite having set to sync and show all calendars. AFAIK events on iPhone is the "most updated" version.
Without going for iCloud or any cloud services (which he simply refuse to use), how to have all 3 calendars sync correctly? Is there a way to export calendars from iPhone and import in iPad?