Calendar freezes on making edits post iOS 18 update

There is another thread on this topic under iPhones. I’ve had the same problem on both my iPad and iPhone, and 18.01 doesn’t help. Even worse: after deleting all of my calendar accounts and all of my email accounts, Exchange and iMap, the calendar was still killing my battery in the background without any data in it. The only thing I could think to do is delete both the calendar and Mail apps, and use Outlook for iOS and iPadOS until Apple fixes this. I did submit a bug.

Same issue with my iPad Pro M4 13" as well as my iPhone 15 Pro Max. Have tried offloading and reloading calendar from storage, uninstalling and reinstalling calendar and showing only our shared family calendar with no tasks, changing from sync all past events to just the last two weeks, as well as multiple forced and non-forced restarts on both devices, signing out and back into iCloud on the iPad, unpairing and repairing my Apple Ultra v2 watch to the iPhone. When try to add any event to the calendar on the iPad the application freezes and then on restarting the app the calendar is blank requiring a reboot. Very similar behavior on the iPhone except for a few times successfully added a test event.

Also calendar app is chewing up my battery on both devices with background activity to the point where my iPad is shut down hoping 18.0.1 solves this issue soon. Soon after the update the phone gave a suspended charging temperature alert but this has improved. After shutting down the iPad a few days ago the phone continued to show that the majority of battery use is calendar background activity but battery drain seemed to be approaching normal behavior but as I type the phone is warm at 47% charge down from 90% with overnight charge after only 3 1/2 hours use showing calendar at 66% background activity/18h 10m. Traveling next week and would be nice to see this resolved prior to the trip.

Prior to shutting down the iPad was also having an issue with mail syncing between iPad & iPhone from my exchange account but secondary battery drain was playing with settings from push to fetch and since returning to push improved but still had to sort through emails on the iPad after deleted them from the iPhone before I shut the iPad down.

Also have iMac Pro 2017 and iMac M3 updated same day as did iOS 18 to Sequoia which thankfully has been painless.

On my iPhone 16 Pro - I think I narrowed down the problem to my Exchange account tied to my calendar. I disengaged it for a bit, as well as all my other accounts. The calendar seems to return to normal function. I added back my iCloud, gmail, yahoo accounts first. Things seem to return to normal. I later added back my Exchange account. Now it seems to be working as normal. But it’s only been a day. The verdict will occur once I return to work Monday & start using it more (especially the Exchange side).

My iPad Pro M4 11” is still having calendar freezes. I’ll need to work on doing the above on my iPad to see if it resolves itself. I’m glad my iPhone seems to be working normally. Although, I cannot say I did anything special besides removing my accounts and adding them back in. FYI - I don’t think NordVPN is the issue either…I’m running it too.

Major I would say. Was suspicious that was the issue as coincident with the exchange email sync issue. Unfortunately use my exchange account for everything except the calendar so hope it’s solved with 18.0.1 and soon.

Guess I was under the delusional impression that they monitored this group. When you say you reset it totally do you mean you reset and restored from an iCloud backup or indeed started completely over?

Steve you are the man!!! Took my exchange account off on both my iPhone 15 Pro Max and 13" iPad Pro M4 rebooted and normal calendar function. Then readded exchange account and still normal calendar function. Hope battery function will normalize will report back if it does not.

Thank you!

The hang/CPU utilization was so bad for me I’ve been unable to remove the Exchange account. Charging also stopped due to overheating. Calendar even hung when simply tapping OK to acknowledge notification of an expected appointment.

I'm on an iPhone 12 mini. I had the calendar freezing, mail was only partially responsive (I could scroll but when I tapped to open an email nothing would happen), and my battery would drain from 100% to 0% in 3 h and the phone was very hot. In fact sometimes it stopped charging because it was too warm and it needed to cool down (despite being in an air conditioned room).

I deleted my exchange account and all of the above issues resolved. After about 12 hours I created a new exchange account with the same account information as before. It took about 20 min for mail and calendar to load all of the information, but the phone seems to be back to normal. Everything is responsive and my battery life is back to normal. I've been testing it for several hours.

Iphone 15 pro, iOS 18.0.1. My calendar isn't working either. Once I type a new event name, I can't click anything, and the app is frozen. Then I have to close out the app. I went onto Chat with Apple and after running through a number of troubleshooting, then said that this was a software issue, that it might not be taken care of until the next update! I need my calendar for work and appointments. My Macbook calendar isn't syncing to the iphone either. They're going to call me tomorrow to attempt more troubleshooting. Super frustrating.

I have had this issue as described and have no choice but to use the Outlook ios Calendar. The main annoyance is you cannot click on a date or time in iMessage and have it add to Outlook.

I have tried multiple reinstalls, deleting accounts, etc. Nothing worked other than leaving the calendar without any accounts connected to it (so just "on this device"). However, this morning the calendar app drained the battery over 50% in the background in 3 hours for no apparent reason. Deleted the calendar app in its entirety has helped in the past and I just did it again. This definitely started with ios 18 as I had no issues prior with multiple calendars pushing to ios app. We are at the mercy of apple fixing this issue and fortunately I am beginning to become accustomed to the Outlook app with the one annoyance that click to add an event from imessage does not work.

I found the secret to deleting the account was to restart the phone and then do it really quickly before the phone starts to sync. You can delete the account from any exchange synching app like mail notes or reminders.

Happy to report I just updated my iPhone 15 Pro Max to iOS 18.1 and 13" iPad M4 to iPadOS 18.1. Full disclosure I only tried adding a few test events to our family shared iCloud calendar on each device and modifying a few existing events but so far no freezes. Hope to see that the battery drain issue with increased calendar activity in the background has resolved too and will report back when I have enough data.

Confirming calendar background activity no longer listed under battery usage by app and excessive battery drain and abnormally increased temperature have resolved on both my iPad & iPhone. Only casualty, other than losing significant utility from devices from iOS 18 till 18.1 and time wasted trying multiple failed interventions to correct issue by myself and with the assistance of regular and upper tier customer support, is a permanent drop in my iPhone 15 Pro Max battery from 100 to 96% maximum capacity.