Iphone Calendar

Hello Andrew_Milano,

Welcome to Apple Support Communities!

If we understand your post correctly, your iPhone suddenly started to show the Japanese calendar and you are unable to use some apps that request dates because the format is incorrect. We'd like to help!

Try the steps provided in the article below for help with the language.

Change the language, time zone, or regional formats used on iCloud.com

What is your language currently set to?

Thank you for using Apple Support Communities.

Take care!

Hey Andrew_Milano,

Thanks for the follow up!

Let's give the steps in the article below a try for help changing the language in Calendar.

Set up multiple calendars on iPhone

Let us know if you have any questions.

Thank you for using Apple Support Communities.

Take care!