Calendar

Howdy Weeder280,

Thanks for taking the time to reach out in Apple Support Communities.I understand in the Calendar app, you'd like to remove the holidays from appearing.

Customizing the Calendar app is an important feature on your iPhone. I'll be happy to help.

You can turn off the holidays from appearing, by following the steps outlined in this helpful article: About holiday calendars on iOS and macOS

Kind regards.

The Holidays calendar is a subscribed calendar. As such it can’t be edited by a subscriber, only by the creator of the calendar. There are thousands of subscription calendars available on the Internet, most of them free, so a search should turn up one that meets your needs. Or just add the holidays you want to your own calendar.

Turn on iCloud sync on all of your devices and all of your calendar apps will sync. Mine do across my iPhone, my iPad, 2 Macbooks, my  watch, my wife’s iMac , her iPhone, her iPad and her  watch.