CalDAV Known Issues
Apple's iCal, Mozilla Sunbird, and Google Calendar differ in the types of event reminders offered. While Google Calendar supports pop-up, email, and SMS reminders, iCal and Sunbird only support pop-up reminders. Accordingly, only pop-up reminders are synced between Google Calendar and these calendar applications.
This feature (iCal File > New To do) will either be unavailable for selection or you'll receive an error when selected.
When trying to create a new (secondary) Google Calendar in iCal, you'll receive an error message. Even though a calendar may appear, it will disappear after restarting iCal.
It's not possible to browse room availability or reserve conference rooms from within Apple iCal or Mozilla Sunbird. This feature is not supported by CalDAV.