Read
From Wikipedia
The ability to view the calendar of other group members (including the chief) is set in two steps:
- user preferences at the admin-module (these settings are not transparent to the user yet).
- not viewable: The calendar is not shown to other user.
- viewable, not readable: Only the occupied times are shown and no content.
- readable: The occupied times are shown and the content text.
- settings of the viewability for single events – refer 3.1.2.2.
The details of an event, shown in the enhanced form, can only be viewed by the owner of the event and the calendar.

