How to Use the iPhone Calendar with iCloud
iCloud stores your data on a remote server that syncs data updates between your computers or iOS devices. Even if you only use Calendar on your iPhone, it makes sense to use iCloud so you have a remote copy of your Calendar in the unfortunate event that something happens to your iPhone.
To turn on iCloud, open the Settings app, tap iCloud, and tap the Calendars switch on.
Any changes you make in Calendar on your iPhone or on other devices associated with iCloud, such as your computer, iPad, or iPod touch, are automatically pushed to all devices.
You can edit the name and color and delete iCloud calendars on your iPhone. Open the Calendar app and then tap Calendars at the bottom of the screen to see the calendar list. Tap the red info button to the right of the calendar, do one of the following, and then tap Done:
Edit the name of the calendar by tapping in the first field, selecting the text, and typing a new name.
Edit the color of the calendar by tapping the color you want to associate with that calendar’s events.
Delete a calendar by scrolling to the bottom of the screen and tapping the Delete Calendar button.