Support:EmailHosting:iCalImport

From Greenview Wiki

You can import your iCal calenders to the Zimbra by first exporting them to a local .ics file. Once you have done this, log into your Zimbra webmail account. Click the Preferences tab, then click Import/Export on the left menu. Click the radio button for "Calender" next to Type. Then click the Browse button and select the .ics file you have exported from your iCal calenders.