Why is my Calendar app not working after macOS Sequoia update?

I posted a week or two ago with the same issue. A few days later i gave in and chatted with apple support, which escalated 3 times until a senior tech called me to work through the issue. Long story short, everything she offered and tried did not work and she was surprised and said she had not seen this before (even though I told her many people in the discussion group were posting with a similar experience). The next day, though, I figured out a fix myself.

Problem: If I launched Mac Calendar on Sequoia 15.2, wheel starts spinning immediately, then about a minute later error message that my mac is running out of application memory. From the list of applications, the calendar is taking 150GB and the number keeps climbing. Only option is to force quit the Calendar.

TLDR -- Solution that did work was:

1) Launch Mac email

2) Click Mail/Accounts. For each account that has calendar activated, disable the Calendar. Even if it says it will delete that calendar from your Mac.

3) Once you're done disabling all calendars accounts, launch Calendar App. That's the first time in a couple weeks it did not require a force quit, because it's not trying to launch and sync any accounts.

4) Now go to Calendar/Accounts, and add one account at a time. When I tried to add all of them, it hung again. My regular huge gmail file (a couple decades worth) loaded fine. That game me hope. My business account loaded fine, so 2 main accounts were working.

5) When I activate my Contacts calendar account (which syncs all the birthdays in contacts so it shows up in the calendar days), it hung and needed a force quit.

No idea how to fix that file, but for now I've just disabled that sync and my calendar app is working again.

Things that did not work that tech support tried with me:

-- disabling icloud sync

-- creating a test user and seeing if calendar app worked (it did)

-- logging in in safe mode a couple times

-- multiple reboots

-- finally, re-installing the OS, still did not work

Hope that helps

Following TKDKidd's advice, it worked for me but with a tweak: To get Calendar to work steady and stable I had to disable Scheduled Reminders from Calendar app on Mac (basically just disable it on the check box on the list of calendar - left menu), which is a pity because looks like a feature I would be pleased to use... I'll hold until Apple fixes this issue... If it will.

Note to whomever may want to try this solution. If your calendar is crashing then you have no way to get inside it to disable the Scheduled Reminders. You'll have to follow TKDKidd's steps: first go to settings and disable iCloud calendar sync, then open calendar (should work; in my case was displaying only the Scheduled Reminders), disable scheduled reminders (result empty calendar, or only non iCloud calendars showing), then on settings reenable iCloud calendar sync, may take a few mins to rebuild the events on the app, finally do not enable Scheduled Reminders (in my case, a few seconds after trying reenable, it crashes again, and I needed to go through these steps once again).

BTW, my scenario: I sync only my iCloud account related calendars (no gmail, no outlook, nothing else). I have several calendars under my iCloud account, some of which are shared with family members.

I also have several Reminders list, some of which also shared with family members.

Both in calendar and reminders I have a lot of recurrent items.

It looks like the root cause may be related with the volume of events to display on Calendar app when trying to combine all events and reminders on the screen.

Hope it helps someone else.

And thanks TKDKidd for the simple but effective tip.

Running on an M1 Mac mini With macOs Sequoia 15.2, and when typing into the Calendar search in upper right it showed "Searching" and would never complete. I restarted the Calendar app, rebooted my Mac mini, turned off Calendar in iCloud and then turned it back on - though still searching was unsuccessful.

Here is what worked for me: In the Calendar app, open the left sidebar to expose all of your iCloud based calendars. Deselect the checkbox of each iCloud calendar, then try a search. Incrementally enable the checkbox of one of your iCloud calendars in the sidebar, then search for something again. Continue to add remaining iCloud calendars one at a time. When all of my calendars were enabled, searching now worked across all 5 iCloud calendars as before. iCloud sync appears to maybe have a bug.

UPDATE: I now have about 98% of my functionality restored. I deleted all five of my synchronized calendar accounts and then added them back. Everything is now synchronizing as it should. I am also able to edit events but only if I double click the event to open the pop-up window and make my edits there. The missing 2% functionality is that I cannot edit events in the right side panel as before Sequoia. Also, no more freezes.

I have found that every time I update my Mac to the latest software upgrade, my Calendar (MacOS Calendar) stops syncing with all my email accounts in Mail (the native Apple one). This drives me nuts and the only solution I have found is:

1. delete my email accounts from Mail: Mail> Accounts then select account and click delete. I have 3 exchange emails, and 2 google based emails - delete them all (seems scary I know; however, all the information is actually stored within the email accounts on their servers so nothing is lost)
2. refresh Calendar: View> Refresh Calendars and the calendars should disappear. ** If calendars do not disappear, restart Mac, reopen Calendar to confirm they are gone then carry on with step 3
3. close Calendar and go back to Mail to add back the email accounts - make sure all the options including Calendar are checked off. Loading the accounts can take a long time (hour+) as Mail has to reload how many ever thousands of emails from the various accounts. Be patient as Calendar is not updated until the accounts are fully loaded. In my experience, if I refresh my calendars while Mail is still downloading it causes issues for Calendar. If I rename my accounts while Mail is still downloading it causes issues for Calendar. I like to think of Calendar as the Head Chef for a 5 star Michelin restaurant - everything must be done perfectly and precisely, else failure.
4. once the accounts are back in Mail (the downloading messages at the bottom of Mail has disappeared - this can take awhile!) restart Mac laptop
5. after the restart Mail opens and I open Calendar and watch as all my different calendars are available in their colour-coded glory as if nothing happened. All events including all past events going back to the beginning of having those email accounts, as well as the future ones are back. More importantly Calendar syncs again! ***Sometimes I have to refresh my Calendars for them to show up, once refreshed they are there and will sync.

This seems like a long process and it is because I have tried to toggle the calendar function off and back on in the various email accounts - that does not work. I have toggled the calendar function off, refreshed my calendar, toggled it back on and then restarted my Mac - that also does not fix the sync issue. The only way that I have found that works for me is to delete the whole account and then add it back - which seems ridiculous, but here we are.

When iCal on my iPhone do not sync with my Mac Calendar - same deal, I just delete the account on my iPhone and add it back.

I have this issue everytime I update and it drives me nuts! The only solution I have found was to delete my exchange/outlook accounts from my calendar (and mail), then add them back. Once they have done their thing of downloading the 80 million messages you can restart your mac. After the restart you can open calendar (and mail) and they should show up. If not try going to calendar>view>refresh calendars. IF they still don't show it might actually take overnight to show up. I have 3 exchange accounts in my calendar and 2 will show up immediately after I delete, add back, restart, but 1 takes until the next day. I have no idea why.

Before I found this method I used to unclick the calendar option in the accounts setting, but it never worked. Now I skip that step and go right to deleting the whole account and adding it back. Is it annoying absolutely, does it work, yes.

Hope it helps you.

In my case, it was a subscribed google calendar that caused the crash. As described above, I stopped synchronization in iCloud, then reactivated it and subsequently deactivated all calendars in the Calendar app (by unchecking them). After that, I gradually reactivated the individual calendars, and one calendar stood out that caused the app to crash.

ok - I thought I replied to this with my fix but it didn't post so here goes again. Good news - when I updated to Sequoia 15.1 my calendar problems of the app locking up went away. I did have a problem downloading the update and it froze 10 minutes in about 4 or 5 times and I looked it up and they told me to reboot into safe mode and then try it and I did and it was able to download and update. This fixed my calendar issues. Yay! 😁

I just updated to sequoia 15.3.2 after months of waiting. Opened calendar and everything was gone. I can't believe this happens with such a late update.

The solution offered by TKDKidd saved me. I unsynced calendar in iCloud, quit calendar then restart.

Still no events but reminders appeared.

I synced calendar again in Iclound, quit calendar then restart. Events were back. Phew...

Really Apple, that was scary.

Here is what worked for me.

in Mail, Click on Mail, then click on Accounts

Select the account that is not syncing correctly and turn off Calendar. It then asked if I wanted to delete all from my Mac, (yes).

Quit mail, quit calendar.

Go back into Mail Accounts and turn back on Calendar.

Annoyingly, it will repopulate the calendar but also send you all of your calendar invites back to you, but otherwise it worked great to do this way and now it is synced.

This worked for me, I have 3 different mail accounts but only 1 was not working correctly with Sequoia since the update.

See my reply above or here it is again...

ok - I thought I replied to this with my fix but it didn't post so here goes again. Good news - when I updated to Sequoia 15.1 my calendar problems of the app locking up went away. I did have a problem downloading the update and it froze 10 minutes in about 4 or 5 times and I looked it up and they told me to reboot into safe mode and then try it and I did and it was able to download and update. This fixed my calendar issues. Yay! 😁

I too was having a problem with Calendar after an upgrade, but I eventually discovered that I had activated Mouse Keys. Once I turned Mouse Keys OFF Calendar reverted to normal behavior as did Libre Office, which had also been adversely affected.

In my case, that was a subscribed calendar with the NFL matchups. I deleted the calendar

Quit syncing with iCloud. Once you do this calendar should open. Then turn on calendar sync with iCloud again. That is what worked for me.