Connect on iOS

Go to Zimbra on you computer
Click the Preferences tab
Click Calendar on the left under Preferences
Scroll to the bottom of the page and check the Enable delegation for Apple iCal CalDAV client box
Click Save
Log out of Zimbra and log back in
Go into settings on your iPhone and select Mail
- On older versions of iOS this screen is called either Password & Accounts or Mail, Contacts, and Calendars
Tap Accounts
Tap to Add Account and choose Other
Choose Add CalDAV Account
For server, enter: zimbra.earlham.edu
Enter in your Earlham username (without the @earlham.edu)
Enter the password for your Earlham account
Enter in a description to identify your account
Tap Next
Tap Save