Instructions apply to iPhones with iOS 12, iOS 11, or iOS 10.
With Yahoo Calendar activated, events appear in youriPhone calendarautomatically.
Setting up Yahoo Calendar and the iPhone Calendar to synchronize in the background is easy.

Any changes to the Calendar updates on both the iPhone and your Yahoo account.
If you have not yet added theYahoo as an email accountto iPhone Mail:
Open iPhoneSettingsand tapPasswords & Accounts.
TapAdd Accountin the Accounts section.

ChooseYahoofrom the list of preconfigured providers.
pop in your full Yahoo Mail address where it saysEnter Your Emailand tapNext.
slide in your Yahoo Mail password underPasswordandtapSign in.

Move the slider next toCalendarsto theOn/green position.
Also move the sliders for Mail, Reminders, Contacts, and Notes.
If not, turn it on.

TapFetch New Dataat the bottom of the screen.
CheckFetch.SelectFetch New Dataat the top of the screen to return to the previous screen.
To remove a synced Yahoo Calendar account from your iPhone:
TapSettingson the iPhoneHomescreen.

TapDelete Accountand confirm the deletion by tappingDelete from My iPhonein the pop-up window.