Retrieve appointments by timestamp with Caldav

[gambo]

I use caldav4j java library to manage appointments in Zimbra.
The problem is that i can't retrieve events by a timestamp range. It returns to me always the whole list.

This is the request that java code execute:

<C:calendar-query xmlns:C="urn:ietf:params:xml:ns:caldav">
<D:prop xmlns:D="DAV:">
<D:getetag/>
<C:calendar-data>
<C:comp name="VCALENDAR">
<C:comp name="VEVENT">
<C:prop name="UID"/>
</C:comp>
</C:comp>
</C:calendar-data>
</D:prop>
<C:filter>
<C:comp-filter name="VCALENDAR">
<C:comp-filter name="VEVENT">
<C:time-range end="20081210T000000Z" start="20080607T000000Z"/> XXX
<C:prop-filter name="DTSTAMP">
<C:time-range end="20071210T000000Z" start="20070607T000000Z"/>
</C:prop-filter>
</C:comp-filter>
</C:comp-filter>
</C:filter>
</C:calendar-query>

Anyone reading this request understand if there is something wrong with Zimbra caldav implementation?