Unable to sync Calendar App after iOS 18 update

This worked! I tried four different solutions prior to this. After it finally synched, my invites showed up in my inbox and I’m finally seeing a couple appointments I was missing. Thank you, Kimowaggs!!

Kimowaggs, thank you! this worked for me, very pleased! (A couple times you wrote the word calculator in your instructions when you meant Calendar 😆) I didn’t even need to restart my phone. You rock!!

After downloading latest update my Yahoo account was popping up with a constant reminder to go to settings and sign in. After signing in all my calendar events coded the color of the yahoo account name have disappeared off my calendar. I'm missing appts and clients. I tried deleting Yahoo from calendar, rebooting and reloading. Still all gone.

Thank you @Kimowaggs! I missed a very important meeting not realizing that my calendar had stopped syncing. No help at all from Apple support, or from general web searching. Your clear guidance helped me finally fix the problem!

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.

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.

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.

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!

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…

My reply was removed due to the version I am using for my iOS, so I won’t mention it. I researched and looked for the default calendar anywhere, and I do not have that option.

Same here. I quit all calendars on devices thinking they would update. Not only no sync now I have lost dates.

I don't see any reply from Apple. Am I missing it?? Same issue. Impacting my business

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.🤷🏻

Same problem. Moved from my old IPad Air 2 to new IPad Air. IOS18. All calendar entries transferred ok but new entries do not show up on my Google calendar.

Me too, Apple 12 Pro max calendar is useless, Apple please fix this!!!!