Calenders and Reminders not working

Hey Lind-Z,

Welcome to Apple Support Communities.

Is this happening with your iCloud Calendar or from a different email account? Make sure changes aren't being made on a different device which is then being synced to this device.

Also, check the web-based Calendar if available when this happens to see if the changes were made there as well. This will help determine if the issue is only specific to the iPhone or happens with multiple devices.

Since software updates include bug fixes, make sure the iPhone is up-to-date which is iOS 16.6 and can be checked in Settings > General > About. If it isn't up-to-date, use the steps below to create a current backup.

1. Back up your device using iCloud or your computer.

2. Plug your device into power and connect to the internet with Wi-Fi.

3. Go to Settings > General, then tap Software Update.

4. If you see more than one software update option available, choose the one that you want to install.

5. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.

The steps are available here as well: Update your iPhone or iPad.

Take care.

Hey Lind-Z,

Thanks for providing those additional details.

Based on the information you've provided, the next best option would be to reach out to Apple Support directly at this link here: Get Support

They'll be able to take a closer look into the issue from here.

Take care.