Apple Calendar Can’t Save Event to Exchange – Fix

Last Updated: Jan 18, 2021

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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!

171 thoughts on “Apple Calendar Can’t Save Event to Exchange – Fix”

  1. Thank You!
    Much better then Apple Support online chatrooms.
    Thank you for the detailed instructions for not so tech savvy people like me!

    Calendar “Null” sync issue has been fixed!

      • Hi Michael, I did the same and it fixed my problem but now I’m having another issue which seems to be related. I’m running macOS 11.1 big sur but this issue started while I was running Catalina.

        The issue is that I am a delegate of an exchange calendar with permissions to view and edit. I can view the events no problem but anytime I try to add an event it appears on ical but doesn’t sync to the exchange server and nobody else can view it; I can’t even view the event from my iPhone.

        Any help would be greatly appreciated as this has been driving me crazy!


        • Hi Patrick,

          I’ve never had this issue but I also don’t have edit privileges on someone else’s calendar. Have you tried creating those events on iOS or with Outlook for Mac?

          • Hi Michael, thanks for getting back to me. Yes I’m able to create events on iOS and outlook for Mac. It’s a problem specific to the macOS.

  2. I had a similar issue to another commenter, where the calendar process would quickly restart. You might want to mention that in your instructions.

    I thought maybe the calendar restarts were related to another app, so I restarted and cleared the cache (quickly). That worked! Although I lost a few events in my Apple calendar that hadn’t yet synced with Exchange.

    I find it quite frustrating that calendar alerts you to a problem with the exclamation point but, as far as I can tell, there’s no way to see what the actual error is. I even tried scrolling through the console logs, but there was never an error recorded.

  3. Not sure why, but Calendar Agent will not quit or force quit thru Activity Monitor. Is there way to do it thru Terminal? Thanks!

    • Hey CL,

      Try rebooting your Mac first. It is also possible, that the process restarts so quick that it appears as if it’s never quitting.

      Alternatively, you can do the following on the command line:

      ps -ef |grep CalendarAgent

      Followed by: kill -9 PID

      PID is the second number you see after issuing the ‘ps’ command.

      • Yeah, I think I have it working now, sort of. I did use Terminal. Two odd things I noticed:
        1) Even after I killed it in Terminal, it showed up in Activity Monitor.
        2) One Exchange iCal entry of a weekly repeating event shows up just as a series of vertical blue lines, no text visible. The same entry for the following weeks looks normal.


  4. Working at home due to Covid-19 and getting frustrated. Found your blog, now all calendars are talking to each other at the first attempt at your fix.
    Excellent and not too scary for a semi-novice to do! Calendar Agent needed a couple of goes to kill off……… but got him in the end ………..


  5. At least, I _thought_ it was fixed. At first Calendar repopulated, _everything_ from my Outlook mail was there.

    And then it wasn’t. Completely blank. What could have happened?

    • You might have to go through these steps a few times and make sure the Calendar processes are all killed.

  6. Thank you for this clear and excellent explanation. It solved the problem on the first try. I cannot tell how much I appreciate the straightforward, step-by-step instructions and a little bit about the ‘why’ of each one.

    Very grateful.

  7. This is much more than a Microsoft Exchange fix for Apple Calendar. This fixes the problem of accepting calendar events from outside calendars. It fixes the problem of calendars not updating from Apple Mail “Add invitations to Calendar automatically” being broken, and sometimes calendar sync problems with iCloud.

    macOS is unix based and unix’s cache system is what normally causes all the malfunctions (that and file permissions). Apple needs to do a much better job in detecting cache file corruption and apps like Calendar should automatically detect problems with caches, delete their own caches, and rebuild. And in that process, they should alert the user to the activity in much the same manner as Spotlight indexes frequently get corrupted and there is at least a slight indication that the system is fixing them (weekly for me).

    Users would complain of resource fork corruption in Mac OS 9 and earlier but macOS (aka unix) cache corruption is orders of magnitude more destructive to the system, causing problems to the degree I have to keep a list of cache files for every app I use and diligently delete them periodically to remain functional. Calendar, Mail, etc are among the worst offenders.

    Too many whiny little art majors at Apple making form a priority over function.

  8. The fix did not work for me with a Exchange Account. Even if I tried several times in a row…..
    However, I applied the mentioned fix, followed by removing my exchange account (System preferences: Internet accounts), and a restart. Added the Exchange account again after restart, opened the calendar and now it Is working! For now at least……

    • I did all of the above plus what you mentioned but still doesnt work. I have had this issue for years. Never have been able to get it fixed. I am getting calendar requests from my husband who is on outlook. Always get the ‘revert to server’ sometimes they save sometimes they do not.

  9. As others have said – many, many thanks for posting this comprehensive guide! I sent the link to a client, who was having the issue, just to show him others have his issue and I could fix it by taking a session on his Mac. anyway, thanks to your clear instructions, he has fixed it himself.

  10. Calendar was not sending invitations – they weren’t appearing in the sent folder in Mail – and no errors were displayed.

    So I followed the first few instructions above. Quitting Calendar, Mail, and killing the CalendarAgent process did the trick. As soon as I restarted Calendar the invitations were sent.

    Thank you so much for writing this blog post Mike!

      • I’m back on your article again, hoping it will allow me to fix the issue of updates failing to apply. I try changing the time of an existing event and apply it to all repeating instances when prompted, but after about 10 seconds it reverts to the old time. :(

  11. Nice! I was beating my head against the wall for weeks, couldn’t sync calendars on just 1 device. The key was going into the library cache. This solution wasn’t presented on any other site I searched. Thanks!

  12. Thanks for the clear instructions. They worked for me yesterday but not today :-(

    I even tried a reboot. I’m really annoyed with Apple right now. This is basic functionality that I use multiple times a day that has been there for years without issue. I fully expect in not to be fixed for a couple of years. If ever. That would completely fit with their usual practice of layering new graphical fripperies and pointless functionality on top while neglecting the basics and not fixing known issues. I’m also mad at myself for upgrading to 10.15 last week and not following my usual practice of leaving it a couple of months at least so that everyone else does the beta testing! There was no problem with this under 10.14.

    Anyway, thanks for the effor you put into this and keep up the good work!

    • There has been a development! I was trying to add events to my work Exchange calendar because that’s what I want them in. It seems that it is possible to add events to iCal calendars though. That makes me think that it could be a Microsoft problem rather than strictly being Apple’s fault. That would please me because while Apple annoy me sometimes I love their hardware and software while I hate Microsoft with a passion for everything they’ve ever produced.

      So I have a workaround for now. Once the event is in my Calendar as an iCal event I can then change it to being an Exchange one by right clicking it. I get a warning that some of the fields will be lost because they aren’t supported by Exchange. I wonder if that might point to what the problem is?

  13. Wow, this worked perfectly for me for a calendar that wouldn’t sync. I kept getting the error message, “the calendar can be refreshed”. Thank you very much!

  14. Brilliant. Worked like a charm. This has always bugged me. Can’t Apple fix this? Or Microsoft? Somebody? Thank you!

  15. Thanks for your article. I work in the setup MBP 2016, Mojave 10.14.6 and Outlook 365. After the last Mojave update to the above named number calendar stopped working to sync with Exchange.

    I followed your steps. I couldn’t delete all calendar activities – it relaunched magically and in the same moment the cash files appeared again although deleted before.

    While looking at the screen and wondering what’s going on the 99th try to delete calendar process worked out somehow – still don’t know why. I deleted the cache files one more time (successfully…), rebooted and voila – it worked!

  16. seems to work BUT in my calendar I still have the “triangle with !” next to the exchange calendar. It also says “Calendar can’t refresh the account”. How can I get rid of that??

  17. Hi. Tried your fix more than 5 times and still the same problem. I have OS 10.13.6 and my company recently switched to Office 365. I run AirMail which attaches w/no prob. iPhone attaches too. Any other ideas?

  18. Ha d a slightly different problem: The calendar appointment info-dialog was stuck open. Rebooting did not help and I could not revert NOR update the appointment, the dialog stayed annoyingly open. Deleting the cache files totally did the trick. Thank you so much.

  19. Also helps for exchange sync problems.

    My exchange calendars stopped syncing with (triangle with exclamation mark). So I deactivate “Calendar” in exchange account settings, did the stuff above, started and set the “Calendar” in exchange account settings back to “on”.

    This solved the problem.

  20. I had to repeat the clean up process twice, restart the mac twice and ended up deleting the exchange calendar and reinstalling it – and then it worked :-). Thank you!

  21. Thank God for people like you who take the time to write clear instructions for these kinds of things! It’s too bad you don’t write the material on the “help” menus! Thanks for solving this issue for me; I was seriously about to throw the device out the window in white hot rage.

  22. Worked for me!! Thanks! (I’m running MacOS 10.13.6, Apple mail 11.5, and calendar 10.0). Only issue is that changes that I’d made locally are lost (but there weren’t that many – and that’s only a mild inconvenience compared to getting my calendar back on-line). Thanks!!!

  23. I updated my OS to 10.13.6 and had also deleted a ton of sub-directories (at Apple’s direction) which were eating up my storage space. The residual bad effect is that my two NON-Exchange email accounts are now messed up. I can open a calendar request but there is no option to accept or reject the invite. Also, I am also no longer able to send outgoing calendar requests from either of these accounts. Clearly SOMETHING got deleted that needs to be reinstalled by so far (after a month) no one at APPLE has figured this out and it is crippling me work-wise. I would be beyond grateful if you had any suggestions for remedying this situation.

  24. I had this issue, and solved it with the above, however I think the root cause is related to duplicate entries. The reason it cannot save it second time is because it already exists so no amount of retries will ever work and revert to server is perhaps not possible as you are you reverting to a copy that is still not written according to the local client as it has it cached. Ignore should work but of course doesn’t which I cannot explain
    maybe Ignore does not clear the cached entry it would need to but just bypasses the error until a retry starts it off again ???

    Anyway this is why I think the “clear cache and rebuild works.”

    anyway maybe this helps someone, and like most I have spent too much time on something that should have been fixed years ok !!!!!

  25. Thanks a lot, it fixed it for me.

    A little history here: My Mac was a totally trouble free machine since 2013 until I had to install HighSierra OS early 2018. And I had no choice because in order to keep doing your iOS development Apple forces you to update XCode, which in return requires you to update the whole OS.

    HighSierra was the first OS which occasionally crashed the whole machine, like any Windows machine. But Windows users are used to these crashes and reboots; Mac users are not. And I noticed that somehow XCode was tightly linked with the OS so if something goes wrong with XCode, it brings down the whole machine. By the way XCode is not a great IDE either like IntelliJ, but that’s another story.

    After such one crash few weeks ago, my Calendar stopped syncing with the Exchange server at work. I had to use the online version for my work. But today I decided to finally try to fix it seriously. And good that these instructions worked right the first time.

    Thank you again.

  26. Didn’t work for me. I followed directions and even emptied cache folder. Calendar process keeps restarting itself even when calendar app is not open.

    • Me too! I have followed all directions very carefully but the CalendarAgent keeps restarting itself. I have had this problem before and I was able to fix it but I think there is some step I am forgetting that will completely stop the CalendarAgent. Any suggestions are welcomed!

  27. Didn’t work. Not sure what to say. Followed the directions and even emptied the cache folder. Calendar agent keeps popping up even though calendar isn’t open.

  28. thanks, this was very useful to fix my syncing issues.

    i’m fairly sure my problem was caused by being disconnected from my work VPN, modifying my exchange calendar event, and then having my password expire before I reconnected to the VPN. after that it never sync’d again

  29. I am new to Mac and I have been unable to get my exchange calendar to sync even though email was fine. Different problem to the one above – I just got a message that Calendar was unable to upload but this fix seems to be a ‘fix all’! Worked brilliantly. Thank you :-)

  30. Yes! My calendar stopped syncing w Office 365 about a week ago, and nothing else worked. Followed your steps and I’m back in business!! Thank you.

  31. This doesn’t seem to work for me, and I’d like to think I really went all-out…

    1. Reboot High Sierra to Recovery Mode (⌘R on boot)
    2. Mount the encrypted APFS volume (e.g. Macintosh HD)
    3. Run Terminal (from Utilities menu)
    4. Command line fun!
    # chroot /Volume/Macintosh\ HD
    # cd /Users/username/Library/Calendars
    # \rm -rf *
    # reboot

    At that point, there’s nothing left for Calendar to use. It has to use the configured account information to recreate everything in that directory, which it does just fine.

    Here’s the problem. I _still_ get four events on one calendar that are not on the server and (more or less strangely) do not appear on my iOS devices. This does not occur across all macOS devices (running the same version), either; one macOS laptop shares the server’s view, the other does not.

    • Hi Don,

      That’s odd indeed. Did you also go ahead and delete the “regular” cache folders as mentioned in, such as ~/Library/Caches.

      Also, have you tried removing the account from System Preferences, then deleting the cache files and re-adding it?

  32. Thank you. That solved the problem but all my events disappeared (half an hour has passed since I relaunched the calendar after deleting the three cache files)

    • Hi Lisa!

      Just quit Calendar again and restart the calendar agent process – or restart your Mac and your events will reappear!

  33. This worked for me (and fingers crossed that it stays fixed!) Thank you for sharing the solution. I’m on a MacBook Air 2015 Mac OS X High Sierra 10.13.3 I use Outlook on my iPhone and MS Outlook for Mac, v 16.9 (180116)

  34. Wonderful advice here, thank you. It worked well on macOS High Sierra (10.13.2) with Office 365 (served locally by my university). But I had to go into Preferences–>Inet Accounts and manually deactivate and activate again syncing of calendars for Google and Exchange before they showed up in Calendar again. iCloud and default local calendars synced on first refresh, though.

  35. Wow this is the second time you’ve saved my bacon with my MacBook! I enjoy your newsletter as well. THANK YOU FOR TAKING YOUR TIME TO HELP ALL OF US! Apple should seriously hire you. :-D

  36. It successfully deleted all of my calendar events, If that’s what the goal was but that’s not what I was wanting to happen. Now my calendar application won’t open.

  37. Hey! Tried several times to follow the instructions, but I still get the same message when I try to invite someone to the event.

  38. Tried the above fix – did not work. I still get this message.

    Calendar can’t refresh the account “——-”. There was an error attempting to send your changes to the exchange server.

  39. Yes, this worked on my MBP High Sierra 10.13.2 – deleted caches then killed the calendar agent – no reboot needed – many thanks!

  40. Hi. This method did not work for me (OS 10.12.6 vs. Office365). The stubborn bad events keep coming, and from time to time – as new event becomes broken – they also aggregate, so I receive these error alerts now in bunches of 11 alerts every time, that I need to dismiss.

    One important hint I have – rather – a scenario I found to reproduce the problem – is when I try to DELETE an event I was invited to, and that I do NOT have permission to delete – i.e. I’m not the creator of that event. It looks like the event is locally deleted from my calendar (at least – visually) but from then on – that even will bug me forever with that nasty alert. Neither “Revert to Server” “Ignore” or anything else will silence this nagging.

    Another point. When I followed your directions (killed both Calendat, Mail, and “Calendar Agent”) I went on to delete the caches – but even before I relaunched Calendar, I’d say – 15 seconds after I deleted those caches – they were recreated on disk. So, I’m not sure we’re killing enough things, or maybe we should shut off something instead of just killing a process.

    Also – Maybe there’s some documentation of how Calendar persists things, and maybe we can just find some .plist, or Directory with all those pesky zombie events – and just delete them from there?

    Any new idea will be appreciated. I’m fed up with these dialogs.

    BTW – I tried much graver methods, like, for example, deleting all my Calendar accounts from the Mac (in the Internet accounts preferences panel) restart, then re-create and re-login each one of them from scratch (my, my @gmail, my 2 exchange accounts, my Yahoo account, LinkedIn, Facebook etc.)

    • Hi Motti,

      It’s normal that the deleted cache files come back immediately, but only if you haven’t killed all required processes. If no related process is running, the cache files shouldn’t come back until you restart the computer or the Calendar app.

      I would go ahead and make sure all related processes are terminated, then remove all Calendar accounts via System Preferences. Next, delete any offending events via (browser) or your mobile phone. Last, reboot and add the accounts back.

  41. Worked for me! Thanks a lot!
    I killed the calendar agent in “Activity Monitor” before and after, just in case!

  42. Worked perfectly.
    I’d add that in Step 4, you need to press the “Option” key and then the “Go” menu in the Finder to see “Library” folder; otherwise this worked like a charm.
    Thank you!! ?

  43. Worked, thank you!
    It is the second time I am repeating this procedure in a month, but at least for a month I had no issue.
    One thing which worries me is that some of my invitees reported that they received my old meeting invites, which is no good. :( Any ideas how to avoid this?

    • Hi Joanna,

      I have had that happen to me before, and I don’t know if there is a workaround. But if I remember correctly, the last time that happened was a few years ago. I never had this issue with newer versions of macOS. What version are you on?

  44. Thanks, this worked for me, I script, so I do not have to recall the fix.

    # close all mail / calendar processes
    # ps xc | egrep ‘Calendar|Mail’ | cut -d ‘ ‘ -f 1 | tr ‘\n’ ‘ ‘ | xargs kill -9
    # trash calendar caches
    # find ~/Library/Calendars/ -type f -name “*Cache*” -exec rm -vf “{}” \;

  45. It worked for me, I could not update my exchange calendar after high sierra upgrade. And I did panic a bit when everything was gone for half a minute. Thanks!

  46. Thank you for the guidance, but I hesitate to try without knowing what I might lose. This issue means that I have event on my Mac Calendar that are not yet on my Exchange Calendar, and vice versa. If I follow the instructions to wipe out cache files, will I lose the events on my Mac that are not on Exchange? In other words, will my Mac calendar be rebuilt using only events on Exchange?

    • Hi Razi,

      You may lose local changes when removing the cache files, as Calendar will try to restore what’s on the Exchange.

  47. It really helped me after I’ve quit the calendar agent. Because I was already hopeless and in the logs there were strange errors that meant nothing on google. I’ve used the same steps to get my google calendar alive again. So thank you alot for this resource.

  48. Thanks for the post, this helped me fix the issue instantly. I renamed the cache files first (appended .old to the name) so if there was an issue I would be able to restore them. Once the calendars refreshed all was well.


  49. So most of these instructions contributed to my fix: I performed the steps IN THE FOLLOWING ORDER and so far, all seems well:

    Delete relevant cache files in FinderGoLibraryCalendars
    Also delete Calendar Sync ClienID Conflicts.tmp (took a punt on this one)
    Quit all calendar processes in Activity Monitor
    Relaunch Calendar

    Events and invitations have all reappeared, and some trial amendments to existing appointments are updating correctly – including updating invited contacts and reflecting the changes on Outlook via FireFox

  50. Like Marina, I get “Calendar can’t refresh events …”. My Exchange calendars show up but will not populate the actual appointments in the Exchange server. I all worked until a couple weeks ago. I use OSX 10.11.6 (El Capitan). Seems to work ok on my iPhone and on another Mac with OSX Sierra.

  51. It worked for me, but I had to quit the CalendarAgent using the terminal…

    I then restarted my Mac, but the Calendar app kept quitting unexpextedly because I hadn’t restarted the CalendarAgent using the terminal.

    Once I restarted the CalendarAgent manually (using the link above), everything started to work fine again.

  52. Nope – tried it 4 times – exchange email works – iCal does not – I am on a mid-2009 MBP running El Capitan 10.11.6. It was working this morning just fine, but then tried to add another (2nd) exchange account and lost all of my original account calendar items. They are out on the web and on my phone, but the iCAL on the mac is conflicted somewhere…

    • 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.

  53. 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?

    • Hi Toby!

      No worries, just repeat the steps and make sure you quite the calendaragent process while doing it. Other users have reported that rebooting the Mac helps.

  54. 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.

    • 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.

  55. 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.

  56. 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.


  57. 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.



  58. Hi
    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.

  59. 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…

  60. 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!

  61. 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.

  62. 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).

    • 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.

  63. 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.


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