How to Clear the iCal Cache

Preparing to Clear the Cache

1. 
   Open the Calendar app. Double-click the calendar icon in your Mac's Dock.
2. 
   Back up your calendar's data. If you have multiple calendars synced to different accounts, you'll need to back those up, too. To do so:^[1]

   1. Click File
   2. Select Export
   3. Click Calendar Archive
   4. Select a save location.
3. 
   Try removing and re-adding the account. You may be able to solve your calendar problem by removing the calendar account from your computer and then adding it back. To do so:

   1. Click the Apple Menu
      
   2. Click System Preferences
   3. Click Internet Accounts
   4. Select the calendar's account.
   5. Click -
   6. Restart your Mac
   7. Go back to the Internet Accounts page.
   8. Select an account provider (e.g., Outlook).
   9. Enter your account's email address and password.
4. 
   Close and re-open your Calendar. If the problem was fixed, your account simply needed a refresh. If not, continue to the next step.
5. 
   Double-check your backups before clearing your cache. There is a decent chance that your calendars' contents will be completely deleted if you clear your cache, so make absolutely sure that you have a backup file for each of your calendars. Only proceed after you are certain that you won't lose anything important.
6. 
   Close your Calendar app. You are now ready to proceed with clearing your calendar's cache.