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How to fix – Apple Calendar can’t save event to Exchange

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In this post, I’ll explain how to fix the pesky Calendar can’t save event X to Exchange Server issue with Apple’s Calendar in OS X or macOS. The issue occurs when the Mac Calendar won’t sync with Exchange and then refuses to accept the calendar data on the server.

Calendar and Exchange

Apple’s Calendar (prev. iCal) in OS X/macOS and Microsoft Exchange do not always play together nicely. At work, we have a bunch of Mac users who had issues with our on-premise Exchange 2010. When we migrated to Office 365 the situation improved dramatically, but I still ran into the occasional problem.

One of the more annoying problems is when Calendar doesn’t allow you to make changes to an event or even delete it. But instead, it responds with the following error message: “Calendar can’t save event X to Exchange Server.

Calendar can't save to Exchange

Calendar can’t save to Exchange

The Calendar app often gives you three options: Revert to Server, Try Again and Ignore. In some cases, neither option resolves the issue, and the error message keeps coming back, every time Calendar tries to synchronize with the Exchange Server.

Note: The screenshot above is for illustrative purposes only. I triggered the error by adding a too large attachment to my test event. Your error message may look slightly different.

How to fix: Calendar can’t save event X to Exchange Server

I don’t know the exact cause of this issue but I can only assume it is related to a corrupted event or individual event data Exchange doesn’t like (i.e., large attachment). If you cannot resolve the problem by any of the three options Calendar offers you, it is time to fix the problem manually.

The solution involves deleting some cache files and restarting all Calendar processes. In a nutshell, you have to:

  • Quit Calendar application (Command + Q)
  • Quit Apple Mail
  • Open Activity Monitor (through Spotlight or Launchpad)
  • Search for “Calendar” and quit all the relevant processes
  • Open Finder and navigate to ~/Library/Calendars
  • Double-check Activity Monitor to make sure no Calendar-related processes are running
  • Delete cache files
  • Relaunch Calendar

Step 1: Quit Calendar and Mail

Quitting Calendar can be done through the keyboard shortcut Command + Q or via the Calendar > Quit Calendar menu. The same steps apply to Apple Mail. It’s essential to quit Mail too because it integrates with Calendar, depending on your configuration. That integration can lead to locked files that you can’t delete or, in some cases, it immediately recreates files you want to delete.

Step 2: Open Activity Monitor

To launch Activity Monitor go through Launchpad (second icon from the right in your dock) or use Spotlight (Command + Space).

Calendar can't save event X to Exchange Server

Launching Activity Monitor through Spotlight


Apple Calendar can't save event to Exchange

Activity Monitor: Make sure you kill all relevant processes

Step 3: Quit All Calendar Processes

Quitting the Calendar application is not enough because there is still a background process running called CalendarAgent that needs to be terminated as well. The best way to do that is through Activity Monitor. Just search for all processes containing the phrase “Calendar” and quit or force quit them all. Once done, leave Activity Monitor running and make sure none of the Calendar processes magically relaunch.

Step 4: Delete Cache Files

Open Finder and navigate to ~/Library/Calendars either through the keyboard shortcut Shift + Command + G or the Go > Go to Folder… menu. There you will see up to three files starting with the name Calendar Cache. Drag all three files to the trash.

Delete Calendar cache files from hidden Library folder

Finder: ~/Library/Calendars

Step 5: Relaunch Calendar

As the last step, relaunch Calendar and don’t freak out if all your events are gone. It will take up to a few minutes to synchronize them back from the server. The cache files you deleted above-contained data from all calendar accounts, not only Exchange. Consequently, all the accounts will have to be synched. Worst case scenario, you may have to terminate all Calendar processes via Activity Monitor again (to force the re-sync) or simply restart your Mac. Rest assured, you did not lose any data!

Alternative Calendar apps

Fantastical calendar app

Fantastical calendar app

If you are fed up with Apple’s native Calendar app, you might want to give Fantastical or BusyCal a shot. I have used twice and never experienced any persistent problems like the one described above.

Apple Calendar can’t save event to Exchange

Some of my readers reported that they had to execute the steps above twice or even reboot before the “Calendar can’t save event” issue disappeared for good.

If the steps above resolved your problem, or even if they didn’t, leave me a comment and let me know, please!

About the Author Michael Kummer

I was born and raised in Austria. I speak German, English, and Spanish. Since moving to the U.S., I have lived and worked in Alpharetta, GA. In my twenties, I was a professional 100m sprinter. These days I do mostly CrossFit. I'm a technologist and Apple fan. I love science and don't believe anything unless there is proof. I follow the Paleo diet and intermittently fast every day. I'm married and have two trilingual kids. My goal with this blog is to share what I learn so that you can spend time on something else.

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  • Marina says:

    Nope, this didn’t work either. I’ve tried working with our understaffed technology department and so far they just say there’s something wrong with my exchange account but offer no solution yet. I also get this message: Calendar can’t refresh events in the calendar “Calendar”. Very frustrating.

  • Nicole says:

    NOTE: I had to restart my computer in order to get my calendar to sync. It didn’t turn out to be a permanent fix (but lasted a few days before I had to do it again).

    • Daniel says:

      Just tried this: to avoid a reboot, you need to kill the CalendarAgent process *after* you’ve deleted the cache files. Otherwise, it just respawns before you delete the cache.

  • Denys says:

    Unfortunately these steps didn’t help me.

  • Sergio says:

    This steps did’t resolve the problem

  • What’s the exact error message you guys are seeing and what version of OS X?

  • sicjoke says:

    My calendar started misbehaving following a migration from Hosted Exchange 2010 to Office365. This worked for me!

    Great little article on fixing an annoying issue.

  • Nathaniel Cunningham says:

    Tried this out, for the error “Calendar can’t decline the event “(null)” on the exchange server”.

    It worked! With one side effect:
    A weekly recurring event that I’ve been part of for the last few months, has now appeared on my calendar *every week stretching back a few years*. It’s easy enough to delete *future* recurring events in Calendar, but I don’t know how to delete a long series of *past* recurring events without deleting the entire series.

    Thanks for the tip!

  • SM says:

    worked – deleted event that was causing sync error has reappeared.

  • Noah says:

    Didn’t Work for me Either. Here’s the message: There was an internal error attempting to save this event. The changes made were not saved.

    • I have had a 100% success rate following those steps but I have heard from users that a reboot in between helped. I was never able to verify that but it’s worth a try…

  • SK says:

    Worked! (for now at least)

  • Alex says:

    This fixed my problem on El Capitan

  • dagosalas says:

    Didn’t Work for me. I’m Sierra OS.

  • Indigo says:

    Thanks, this worked for me on Sierra and cleared out some duplicates as well.

  • Dave says:

    Didn’t Work for me. I’m Sierra OS.

  • Erick says:

    doesn’t work

  • CTM says:

    This worked for me.. Thank you

  • David says:

    Didn’t Work for me. I’m Sierra OS 10.2.2 and office 365

  • jelle says:

    It worked for me, but only on the second go: I did first kill the Agent and then the cache files but they reappeared and that was (I think) because I did not also terminate Mail. (Would it have to do with the fact that there were calendar invites in my mailbox?) Because it also created a mail-cache file *in* the Calendar library. I quit mail, killed the Agent, deleted the cache files including the mail-cache-thingy. Then it worked.

  • Mike says:

    Thanks, man! It works.

  • Rezon says:

    Thanks Michael Good Job?

  • RangerBob316 says:

    Worked for me for about an hour.
    I also see an ” ! ” inside a triangle box next to my exchange account in Calendar. Since it appeared, the sync has stopped working once again. Any ideas? Only way to fix is to repeat your steps above.

    • Hi Bob!

      If one of the events in your calendar is corrupt, you need to delete it and then clear the cache as described in the article. Look out for events with large attachments, as those have caused issues for me in the past.



  • Ben says:

    Thanks. It worked!

  • gabriela says:

    Hi- I just did all that, but It wiped ALL my calendars out. It’s been over 5 minutes and I have no events on my calendar. How long does it take to resync? HELP!

    • Hi Gabriela,

      As confirmed via Email, a reboot fixed your disappearing events issue. That usually happens when you don’t kill the Calendar Agent. A reboot restarts that agent and thus fixes the issue.


  • Posey says:

    YES! My problem was that exchange wasn’t syncing with iCal. I could create events just fine in iCal, but they wouldn’t show up in my Office 365 calendar, and vice versa. I originally deleted all the cache files and that cleared out the iCal, but then I couldn’t add any of my calendars back in (exchange, iCloud, subscribed calendars). I would take the steps to add them but nothing would happen. It wasn’t until I did the Activity Monitor step and then rebooted (before the cache files regenerated themselves) that everything came back perfectly.

  • Fernando says:

    Worked great! Thanks for the tip!

  • maryam says:

    thank you Michael. It resolved my issue with ical, I can now attach files with no problem.

  • mjk says:

    worked for me! thanks!

  • Arlynne says:

    Thanks for this write-up. Unfortunately, it was not successful for me. Any ideas? I’m on Mac OS 10.12.5 on a late-2016 Macbook Pro.

    • Carl Johnson says:

      Same problem here, just occurred. Have tried all these steps and several others, and just can’t seem to get either Calendar or Mail to talk to my Exchange server anymore, even though Outlook for Mac 2011 is working just fine, as are my iPhone connections.

  • toby pearson says:

    that removed all of my calendars!

  • Jan says:

    did it for me!

  • Dirceu Pavon says:

    did not work. Mac Os Sierra 10.12.5 and office 365 exchange online

  • Valter Rodrigues Roldao says:

    Hi, I’m experiencing the same error while syncing with exchange for office365. using Sierra. Although I’m able to download the events I cannot add new events from calendar. When I try I get the message “Calendar can’t save the event … to the Exchange server.”
    I’ve followed the steps, even tried to restart the computer after deleting the cache files, but nothing worked.
    Anyone who tried anything else and worked?

  • Gerry says:

    I upgraded to Sierra (OS X 10.12) and the problem went away.

    • Craig says:

      Well, after trying everything suggested, Gerry’s post did the job for me. Duh, all I had to do was upgrade from 10.5 to 10.12.