How to Use an iPhone Calendar with iCloud
iCloud stores your media, documents, and data on a remote server — called a cloud — that pushes data updates to your iPhone and any other computers or iOS devices you have associated with your iCloud account.
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, do the following:
Tap Calendars 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 will never have conflicting information again!
You can edit the name and color and delete iCloud calendars on your iPhone. Tap the Calendar app on the Home screen and then tap Calendars at the bottom of the screen. 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.