Open the Calendar app on your iPhone
Tap Calendars at the bottom of the screen
Tap the info icon next to the calendar you want to share
Tap Add Person
Enter the person’s email address
Tap Add
Choose the permission level if prompted
Tap Done
Ask the person to accept the invitation
To share a calendar from iCloud, make sure Calendar syncing is enabled in iCloud settings
To stop sharing, open the calendar info screen and remove the person from the shared list