Unable to sync Calendar App after iOS 18 update

I finally figured it out! Go to settings- scroll to bottom and click on Apps. Click on the Calendar app. Click on Calendar Accounts to show all the accounts you have synced. Click on the first account that is not synching correctly. Toggle off the calendar. Let it delete (don’t worry it will just unsynch it). Then back out of settings. Repeat with all accounts that aren’t working. Restart your phone (not sure if necessary but I did this). Then go back into settings-Apps-Calculator-Calculator Accounts- and turn back on all the calendars for the accounts you turned off. They will take a bit to synchronize but worked perfect. FINALLLLLY!!!

I had a similar issue, but a little different. Doing a search would only show upcoming events that I’ve recently entered. I could not search for past events …. but all past events I’ve entered DO show on my Gmail calendar. I did not have a problem searching past calendar events prior to V18.1. After many frustrating days trying to fix this…. I found something that DID work for me this morning. Here’s what I did on my iPhone 16 Pro using V18.1

(Note: I use my Gmail calendar as my default)

• Go to “Settings”, scroll to the bottom and select “Apps”

• Scroll to Calendar and select

• Scroll down to Default Calendar and select

I changed my default calendar from Gmail to iCloud Calendar… then select <Back (Top Left On Screen)

• I closed “settings”, then opened my Calendar and verified my Gmail calendar entries are no longer shown

• I rebooted my iPhone. Then I changed my calendar back to my Gmail account

• Go to “Settings”, scroll to the bottom and select “Apps”

• Scroll to Calendar and select

• Scroll down to Default Calendar and select

• I changed my default calendar back to Gmail.

I opened my calendar and it started populating all my calendar events. And now I AM able to search past events in my GMail calendar. Hopefully this will continue to work for me… and maybe my steps will assist with others having this same problem.

I had the same problem after having to get a replacement phone (and update to ios 18). I just solved it by going to the calendar on my phone, clicking on "calendars" and at the top of the list of calendars was a "verify account" line. I clicked on that, and it was all I had to do. Went back to my PC and hit refresh, and I found it immediately matched my phone.

Hope this helps!

ok 1 more thing that FINALLY fixed the non-sync vanishing entries on my iPhone 12 vs iPad Pro (both running 18.3.1)

Followed all the steps as per Apple Support, then realized the iPad had 3 accounts vs iPhone’s 2. The iPad accounts were iCloud, my ISP’s email, and Gmail, which I never use, so deleted that, then backed out, restarted both devices and BOOM / fixed!

may this revelation be of some comfort to those similarly afflicted…

Turns out, issue with my calendar was two-fold ... iOS upgrade AND I hit the 50,000 maximum allowable calendar entries in iCloud. Be forewarned that you can unwittingly hit the max and then everything stops working.

Unfortunately, there's no way to back up and delete by date. Only options are to delete item-by-item OR an entire calendar which I could never do because I'm so reliant upon the ones I already have. It's a definite shortcoming of Apple's.

Regarding my reply from 3/1/25:

"Thank you Kimowaggs. This worked.

BUT for those who have been modifying events and adding notes to them for MONTHS on their iPhones before they worked out they were not getting synched to their Google web calendar (like I did):

BEFORE you delete your google account calendar from your phone (the "Toggle off the calendar" step) DO SCREENSHOT all new events that you can remember have been entered into or modified using your iPhone since it stopped synching with your Google account, because this data is ONLY ON YOUR PHONE version of Google calendar, and will be lost when it is toggled off and deleted and replaced by the older data from the web Google calendar when you toggle it back on again.

I am grateful to have my iPhone synching with google calendar again, but I am also grateful that I thought to screenshot the recent data from my iphone, and I have been able to re-add it to the restored and now synching google calendar."

My gratitude has been short lived. I updated to the latest iOS18.2.1 last week and stupidly was too busy to check that it didn't ruin my shared google calendar synch, and sure enough, now a week later I have repeated my previous mistake and updated a heap of events in the calendar my siblings and I rely on to coordinate our elderly mothers care, which we share, ie my google calendar.

It did cross my mind briefly but I perhaps foolishly thought the latest update would have ironed out this critical issue for many users. So now I have to try and remember all the updates I've done so I can screen shot them again on my phone and re-type them after I have applied this solution again and lose all the calendar update data I've done on my phone since the iOS update killed my synch again.

I am beyond annoyed about this. This shared calendar workflow has worked perfectly for several years and now since iOS18 it is playing up. I am also getting my apple calendar having spasms as well. Today I looked at it to tell someone what the date of the first Thursday in February was and it was not until I got home that I realised it had been showing the events and dates for January under the February month banner. This has nothing to do with synching to Google calendar so something is fundamentally, yet sporadically, broken in Apple Calendar synch since iOS18.

I logged into my google calendar via web browser and then went back in via the app and it had synced everything.

haven't tried to add any events yet to see if it automatically syncs.🤷🏻

I fixed it

After weeks of this problem of not synching since the iOS 18 update, and hours with senior support, I found the problem and solution.

there was a trojan virus on the Mac.

bit defender is free on the app store

run a deep system scan, and see if you have a virus, removed and then everything was perfect again.

Mac support never even thought about a virus, because they are told that it cannot happen when the new OS is installed.

so I educated them and hope they pass on this solution and tell people to check for viruses more often.

For those of us on this thread having the inability to sync the iPhone or iPad using iOS18 to Outlook through iTunes, I can only surmise that Apple, even though I've seen no comment from them on this thread, has phased out the Calendar function.

I had iCloud for windows on my PC already, but when I flipped the switch to sync Contacts and Calendar items to Outlook, it errored out saying I had no default profile. This was untrue.

SO, Here is what I did to make sure I lost nothing in the process:

On the iphone, I first switched on the Contacts and Calendar items to go to the iCloud. This would insure that all my stuff was synced to the server before moving on.

I made a backup of my Outlook data to a backup.pst file

I had to completely delete iCloud for Windows. Then rebooted.

Ran the setup for iCloud for Windows, and it went through the entire process of setting everything up, from Photos, to Files, etc. When it got to the Outlook portion, it took a couple of minutes to do it's thing, but was thankful I began the process on my iPhone first.

Once this was done, I lost nothing, but I will miss the ability to use iTunes and not be relying on a 'cloud connection'.

There is an alternitive to iTunes that will cost you $40 if you google "Programs to sync iPhone with Outlook"

Thank you Kimowaggs. This worked.

BUT for those who have been modifying events and adding notes to them for MONTHS on their iPhones before they worked out they were not getting synched to their Google web calendar (like I did):

BEFORE you delete your google account calendar from your phone (the "Toggle off the calendar" step) DO SCREENSHOT all new events that you can remember have been entered into or modified using your iPhone since it stopped synching with your Google account, because this data is ONLY ON YOUR PHONE version of Google calendar, and will be lost when it is toggled off and deleted and replaced by the older data from the web Google calendar when you toggle it back on again.

I am grateful to have my iPhone synching with google calendar again, but I am also grateful that I thought to screenshot the recent data from my iphone, and I have been able to re-add it to the restored and now synching google calendar.

Hi there,

Just wanted to share what worked for me, in case it works for anyone else with calendars not syncing between devices. I got a new iPhone and realised that one of the calendars (gmail) was not syncing with my old iPhone or MacBook. I’ve connected my new iPhone via cable to the MacBook and started changing past events which had not previously synced in the Calendar on MacBook. In a matter of minutes all of them synced automatically! I’ve checked the Calendar on my old iPhone and all the events automatically synced as well!

Good luck!

May need to accept the terms of use for new update … should be in the account portion of the iPhone

I DID have success with contacts, finally. From settings / contacts / contact accounts / exchange, uncheck contacts. Then force a reset of the phone and when it comes back online navigate back to the same place and re-check contacts. THEN on the contacts settings scroll down and change default account to exchange. Now when you go to contacts / lists you should see exchange and your contacts populating. I’ve got 3300 contacts it was fun to watch the number of contacts grow until it was done and now I’m ok. While the calendar issue is SO frustrating and apple support acts like I am the only one with the issue, It just has to be an ios18 issue and fingers crossed it will get resolved with the new AI update at the end of the month.

My calendar is having similar issues. (IOS 18.0.1 Iphone 16)

I turn it on, and it doesn't even know what day it is. It thinks it is October 1 when it is really November 10.

I add an event to my calendar, and it does not appear. But when I search for it, it comes up in the search.

When I delete an event and "all future events", it deletes past events as well.

It is behaving as though my calendar does not know what day it is. I click on a day with a colored dot, and it does not show me what is there.

This phone is brand new, and not being able to use my calendar to reliably track my appointments is crippling.

I was afraid to delete my iCloud calendar but it worked! My calendar is repopulating