iOS 15.1 Calendar app is laggy and unreliable

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)

Adding my name to the list. I’ve got several Exchange accounts, a couple of Google accounts and an iCloud account all connected, but I only have the issue with one of my Exchange accounts. If that is unselected in the shown calendars list (so I still have the account and it’s still syncing the calendar AND alerting on events), then the calendar is as responsive as normal. Show that calendar though and it all becomes very laggy. This is my main work calendar so there’s probably lots of events with a large numbers of attendees which the other calendar likely don’t have. Not sure if that’s consistent with other’s experience?

Experimenting with my own setup (Gmail+Exchange+iCloud) it seems like it's definitely a problem with Exchange. If I deselect my Exchange calendar from being show, the problem goes away altogether. Which is a bummer because my Exchange calendar is the main one I use.

I am experiencing similar issues with the calendar showing appointments on the wrong day and such. What helped me was to briefly activate the flight mode, after deactivating it the calendar is back to normal. Hope this helps.

This issue is devastating to those of us that live by our calendars.

That aside, I’ve found that just tilting your phone to landscape, which shows the split view of your day on the left and an individual meeting details on the right, reloads the view and “most of the time” got me the correct events.

This same view works on iPad too, but you have to select Day view instead of Week or Month to get this same view on an iPad. On my iPad I can select Day view and my events show, select Week mode again and they all disappear.

Doesn’t work for me every time, but a lot better than it was. Still needs to be fixed BIG TIME.

One thing that I have figured out is that if you toggle off the calendar for the Exchange account on your iPhone, it fixes the issue if you have that same Exchange account on an iPad and/or Mac. In other words, those seem to operate just fine if your iPhone Exchange account is turned off. What is strange is that ir doesn't work the other way around. Thus, I surmise it has something to do with the Exchange account on the iPhone.

jpetrosoc wrote:

One thing that I have figured out is that if you toggle off the calendar for the Exchange account on your iPhone, it fixes the issue if you have that same Exchange account on an iPad and/or Mac. In other words, those seem to operate just fine if your iPhone Exchange account is turned off. What is strange is that ir doesn't work the other way around. Thus, I surmise it has something to do with the Exchange account on the iPhone.

Great that you've found a solution. But, as a data point, I have an Exchange calendar enabled on my phone and do not have this problem.

PROBLEM FIXED FOR ME: As per my initial post, after deleting a recurring zoom meeting invitation from my calendar, my calendar has and continues to work as it did prior to installing the latest upgrade. I have no idea why deleting this recurreing meeting with an embedded zoom link would have any effect, I'm just happy that my calendar is no longer laggy.

Try rebooting phone! 

For iPhone X onwards press the volume up button then immediately press the down then hold the off button until the screen goes dark and then you see the apple Logo!

If before the iPhone X then hold the off and home button till it turns off and the apple logo appears!

This issue is fixed in iOS 15.2. Here’s an excerpt from the release notes: “This release also includes bug fixes for your iPhone: Calendar events may appear on the wrong day for Microsoft Exchange users”

I Have the same issue with both outlook and goupwise accounts in my icalendar, but not in my Mac calendar. I have tried a lot and now have found a work around (not fix) that seems to work for my icalendar. When I disable all non icloud accounts in my the calendar app on my mac, then suddenly all accounts on the the icalendar on my iphone and ipad synchronize at proper speed. Until Apple comes with a real fix, I am prepared to work without the outlook accounts in the calendar on my Mac as long as the calendar on the iphone remains speedy.

The original bug - where the calendar was slow to render the events - is fixed in the most recent release of MacOS and of iOS.

My last response was to somebody who had posted that the Calendar program would just not start up.

Coachdj1313 wrote:

Has anyone seen this resolved or gotten a fix from apple yet? January 2022 and I’m still experiencing this same issue with my calendar.

If you go back and read the thread, you'll see that most people who've updated to iOS 15.2 seem to have had the issue resolved.

Installed outlook as workaround that works. Fully unacceptable obviously and first time iOS really lets me down.

Working fix for me was to install the Google calender app and let it access exchange account while I wait for fix. Obviously not the best option but it works for now