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iOS 18 Calendar app hangs regularly with Exchange Server

I'm seeing problems on both my shiny new iPhone 16 and my M1 iPad Pro. Initially the issue was super-high CPU utilization (enough to make the phone really warm). To fix that I removed the Exchange account, removed the Calendar app, and then re-installed both. That seemed to fix everything up.


However, this morning I tried to add a new calendar entry on my Phone and was unable to complete the entry. It just hung the app. Couldn't cancel it, couldn't do anything with the Calendar app except force kill it.



iPhone 16 Pro, iOS 18

Posted on Sep 24, 2024 10:34 AM

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Posted on Sep 24, 2024 8:18 PM

After wrestling with it further I've removed both mail and calendar from both devices and installed the MSFT Outlook app. No more hangs or high CPU utilization. May revisit after 8.1 comes out if anything mail/calendar is addressed and announced.

10 replies

Sep 28, 2024 10:36 AM in response to Nick_W_

Glad I'm not the only one, but wow...your problem sounds worse than mine.


Here's a thought: Power cycle the device, and as soon as you login, disable wifi (and cellular if you have it). I had to do this at some point during my futile exercise with this. Once it's disabled, you might be able to remove the Exchange account. Also worth trying just disabling Calendar in the Exchange account sync before removing the account. I still have the account on my ipad with "calendars" disabled. Then reboot again.


At the moment both the Calendar and Mail apps are removed on my ipad and it seems to be working OK. Using MSFT Outlook app for Calendar and Mail.


Also, I had the calendar app hang when tapping OK to acknowledge stuff as well. Something is definitely a bit awry in the Calendar app.

Oct 6, 2024 10:22 AM in response to BennSc

I had this issue too…first with iPhone 15 Pro after iOS 18 upgrade, then again on iPhone 16 Pro. Narrowed it to the exchange server connection I use for work. Work requires a Hub app that installs a profile used to confirm 2 party authentication. Calendar would freeze, regardless of exchange calendar or iPhone calendars. That would put the phone processor into overdrive, heating it up while draining the battery. iPhone restarts stopped the drain, but who likes rebooting that often. This affected my iPad Pro M4, too. So two iPhone versions & an iPad. I have another iPad w/o the exchange connection that has operated w/o issue.


My solution - completely removed the Exchange connections. A few reboots in between, then reinstalled the exchange connection. That solved my problems. My calendar app is working as it should with all the new functionality if iOS 18. I’ve read on other posts whom have done similar actions, but had the issue reoccur later. But so far, I’m okay (knocking on wood as I write this). It’s weird. Most of my work colleagues use iPhone and the same exchange connections. I’ve not heard anyone else complain about this issue. However, I’m normally one of the early adapters of new hardware and software releases, which maybe explains why not many others have complained about this issue. Keeping my ears open…hope this helps you.

Oct 5, 2024 9:00 PM in response to Nick_W_

Same problem here with iOS 18 and 18.01. It continued eating my battery to the point where my iPad died from lack of charge overnight.


I also had to disable all of my exchange Mail and calendar accounts, and fall back to Outlook (which has less functionality). I had to turn on airplane mode, reboot, then delete the accounts to get it to stick. (as BennSc noted). I also reported the bug to Apple. I hope they fix it soon!

Oct 7, 2024 3:01 PM in response to Dennis A.

Just an update: I had deleted all of my calendar and email accounts on my iPhone and iPad, and things seemed fine. However, yesterday both devices had their batteries draining rapidly, and it was due to the calendar app… Even though there are no calendars connected to it. The best fix I could come up with was to delete both the email and calendar apps from my phone.


What a pain.

iOS 18 Calendar app hangs regularly with Exchange Server

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