“Calendar can’t save the event … to the Exchange server. There was an error attempting to send your changes to the exchange server” – I faced this error in iCal for my Exchange calendar with three options (Revert to Server, Try Again or Ignore) and was unable to Save Calendar to Exchange Office 365 in iCal in OS X 10.10 Yosemite . I finally found out that removing the Time Zone Support cache can solve the problem.
How to delete the Time Zone Support cache in Mac OS X?
Firstly, you should check to make sure that your hard disk is visible in Finder: Open Finder > Preferences > Check on ‘Hard disks‘ under Sidebar tab.
- Access your “Macintosh HD” from Finder window > Open Library:
- Open Cache folder and delete the Time Zone Support cache file: