iOS 15.1 Calendar app is laggy and unreliable

Lots of places quoting Apple

saying

This release also includes bug fixes for your iPhone:

• ...
• Calendar events may appear on the wrong day for Microsoft Exchange users

e.g.

https://www.macworld.com/article/547488/ios-15-2-features-release-how-to-install.html

The update has gone to 2nd release candidate so should be out to the public maybe as early as tomorrow

Finally I found a workaround after lot of trial and errors including uninstall & reinstall calendar App. Option is to Unselect Day view and go by week view. This will have better performance and no lag.

The part the really stinks is the data overlapping when swiping between days. I can’t tell what’s real and what isn’t. I have to touch the actual meeting for it to refresh or close and reopen the app. At least if the data was correct and it was just laggy it wouldn’t be as bad. Also, it does appear to be some cache issue. In list view when scrolling into future dates it lags, but if I scroll back up and then back down it’s fine until it gets to new data and it starts lagging and refreshing. I don’t care how big the calendar data is, this worked fine until 15.1.

I have the same problem and it is occurring on both my iPhone and iPad calendars, occurring only after installation of 15.1. Oddly, Apple support recommended I do a full restore on BOTH devices not seeing that the likelihood is the software itself not a faulty installation when it is happening on both devices.

I use both devices for work and the calendar is a central function of that work. It is barely usable now.

I am having the same issue on my iPhone 12 Pro.

I have found a sort of workaround to get the display to act normally.

When you are looking at a day in your calendar and you are sure it is displaying incorrectly (or just want to be sure) switch to Dark mode and back to light mode (or whichever the inverse is).

In my case I have dark mode controls in my control centre so it is a quick couple of swipes.

The issue as I said, is knowing that your calendar is displaying incorrectly in the first place...

I am having the same issue, but my issue is due to my work Exchange account. Tested removing all accounts:

1 Outlook (that has 2 iCal subscribed)

1 Exchange work

When I added all except Exchange back it worked just as before 15.1. When adding the Exchange account back (after running without it for a while) the issues started happening again.

Additionally, it appears to carry calendar information from one day over to display on another day when swiping from one day to another. This makes it even more of a critical issue for me as the dates/times of appointments not only don't display, but often display incorrectly. It is a blocker and I cannot rely on my iphone calendar.

Creating a new appointment is almost impossible.

After entering the first letter in the title, the calendar hangs for 20-30 seconds. If you still enter further letters, they appear only after these 20-30 seconds. If you click on another field (place or time) the calendar hangs again for 20-30 seconds. Thus it takes 5 minutes or longer until an appointment is created.

Furthermore, the appointments are often not displayed correctly in the day view. Often not correct titles are displayed, titles of other appointments. If you touch this title, it jumps to the correct title and if you touch it again, the wrong title is displayed.

I have the problem after the update to 15.1 on my iPhone 12 Pro max and on my iPad Pro. My wife also has the same problems on her iPhone XS max after the update.

Unfortunately, restarting the device does not remedy the situation.

The calendar is currently unusable !!!!

Apple Support in the Netherlands listened to me and found multiple reports of the issue, so for sure the issue is recognized now within Apple as related to use of the Calendar with an Exchange account.

The only suggestion was to see if removing my Exchange solved the issue, which I refused as it makes no sense to test with an empty Calendar.

There is no solution yet.

If you're having this issue, please, report it to Apple via the Support app on your phone. This is the best way for them to see the impact and ensure they have all the right logs. Push to get the case bumped up to a Senior Advisor.

I have found that Calendar is now sucking huge amounts of battery in "background activity" - it used almost 3x as much battery in 30 minutes in background activity as the same time I was actively scrolling through FB (72% vs 27% respectively) - that 30 minute period equated to over 20% of total battery charge drained...

Same issues here! Lagging. Appointments sometimes off by a day. Huge battery drain. Guessing it's something to do with exchange account from my work email. I've logged issue with tier 2 support. Submitted examples and they acknowledge it's a known issue.

Same to me on 15.1.

The problem is persisting if there is any Exchange calendar in mail accounts.

When I removed Exchange account from accounts on my iPhone, the calendar worked fine - no lagging. Not good due the Exchange is my work mail

I'm not sure it's just Exchange.

My wife has only set up a standard Gmail account on her iPhone XS Max (via Add Google Account) and the same calendar problem occurs.

Does anyone know if this is also Exchange or is IMAP being used?

Same here. I completely removed all exchange and other non-Apple calendars from the main Calendar app and now is stable and not chewing battery power! No big issue for me as I was running Outlook for exchange anyway (but still a small inconvenience until they sort it out)