With Yosemite Ical failed to sync with Exchange Calendar.
In my iCal first day of the week was configured to Monday and in Exchange it was Sunday (default). This worked fine till Yosemite upgrade.
I have adjusted "first day of the week" in Exchange calendar to Monday using the browser access.
In preferences I have removed the Exchange account and configured the account again.
Open Ical and syncing should be working fine again.
Thanks to other contributors that solved this by removing the timezone file in the library, so i went for more detail in both calendars.
In both iCal and Exchange calendars, first day of the week is configured to Sunday. I've removed and re-added the Exchange account multiple times. Email working fine. Exchange calendar events still are not showing in iCal. Following the Yosemite upgrade some Exchange events failed to show in iCal. Removing the exchange calendar and adding it back again has resulted in no events showing in iCal. I'm at my wits end and about to switch to Entourage if nobody can solve this.
I do agree that what seems obvious is causing so many disappointments. I also could not believe this been an overlooked issue by Apple or MSFT.
With hosted applications servers can be setup in different timezones, so check the timezone setting for both applications.
Then check the "the first day of the week" settings in both apps.
Then close both calendars.
Go to internet accounts remove the Exchange account. Eventually shut down your Mac and restart again.
Add the exchange account and select the services you want to use.
Start the calendars and test.
Syncing is flawless since I performed this sequence.
Maybe the exchange version can the cause of the trouble.