Your Google Calendar will now appear in iCal’s list of calendars, and changes you make to your Google Calendar calendars in iCal will show up in Google Calendar.
Event information will automatically refresh every 5 minutes. You can change this interval by opening the iCal > Preferences > Accounts menu and selecting a new refresh interval under the ‘Refresh calendars’ drop-down. Keep in mind you can also force a refresh by selecting a calendar and pressing the Apple and R keys at the same time.
Remember, you can only add calendars that you’re allowed to make changes to in Google Calendar.
Calendars that are checked but disabled have already been added to iCal – you can remove them from within iCal.
That’s very cool !