How do I sync my Google calendar with my iPhone?
So I want to be able to add appointments/events/tasks on either and have those changes reflected on both.
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You should really use Google Sync for iPhone to have all the benefits of Calendars (and even Mail if you need it).
In iCal, add a new CalDAV account.
Server Address: www.google.com
Server Path: /firstname.lastname@example.org/user/
Use SSL: CHecked
Make sure you have sync enabled in iTunes.