iphone 5c calendar flashing

Hello paulafromred oak,

Welcome to the Apple Support Communities!

I understand that the Calendar application on your iPhone is not behaving as you would expect. To troubleshoot this application I would suggest closing the app completely and then restarting your device. After the restart, open Calendars fresh and test. Please let me know if the issue continues.

Force an app to close in iOS - Apple Support

Restart your iPhone, iPad, or iPod touch - Apple Support

Have a great day,

Joe

Hi paulafromred oak,

If the issue with Calendar is still ongoing, it may be necessary to completely reinstall the iPhone Operating System. To complete this task, please follow the steps located in the attached article. This will reinstall the latest version of iOS without erasing any data.

If your iPhone, iPad, or iPod touch doesn't respond or doesn't turn on - Apple Support

1. Connect your device to a computer and open iTunes. If you don't have a computer, you can borrow one, or go to an Apple Retail Store or Apple Authorized Service Provider for help.
2. While your device is connected, force it to restart. Press and hold the Sleep/Wake and Home buttons at the same time. Don't release when you see the Apple logo. Keep holding until you see the Recovery mode screen.
   
3. When you get the option to restore or update, choose Update. iTunes will try to reinstall iOS without erasing your data.
   

iTunes will download the software for your device. If it takes more than 15 minutes, your device will exit recovery mode and you'll need to repeat steps 2 and 3 again.

Best,

Joe