How to Sync a Calendar Between Two iPhonesby G.S. Jackson
Apple products share an internal calendar application users can use in conjunction with Apple's iCloud cloud-sharing service. You can create different calendars that represent different types of appointments. This serves as a great way to back up and share different calendars with people who need to know what you are doing. By making sure that your iPhone is associated with an Apple ID and iCloud account, you can create and share your calendars with other Apple iCloud users, who can then access the calendar on their Macs or iPhones.
On the iPhone containing the calendar you want to share, tap "Settings" then "iCloud." Enter your Apple ID and password to activate iCloud.
Tap "Calendars" in the iCloud settings page that appears to turn on Calendar sharing.
Repeat iCloud activation and Calendar sharing for the other iPhone.
Open your Web browser on your computer, and navigate to icloud.com. Enter your Apple ID and Password when prompted.
Click on the share button next to the calendar name when the main Calendar app screen appears.
Click the "Private Calendar" checkbox. Enter the Apple ID associated with the second iPhone.
Click "OK." The second iPhone will have access to the shared Calendar. Both phones will now share the Calendar in real time.