Zimbra and caldav4j java library

[gambo]

I try to use caldav4j java library to insert, update,delete and retrieve events.
I can insert, update and delete events, but when i try to retrieve events from calendar happens a weird thing.
I can't retrieve events by timestamp date.

For example:

Calendar: BEGIN:VCALENDAR
VERSION:2.0
PRODID:Zimbra-Calendar-Provider
BEGIN:VEVENT
UID:20081008T150540-816d9e5c-1a4a-4b8d-ba71-6a531c8c13b8-topolino
SUMMARY:Puccettone
DESCRIPTION:Ti ho cambiato
DTSTART:20081008T134200Z
DURATION:PT3H
STATUS:CONFIRMED
CLASS:PUBLIC
X-MICROSOFT-CDO-INTENDEDSTATUS:BUSY
TRANSP:OPAQUE
X-MICROSOFT-DISALLOW-COUNTER:TRUE
DTSTAMP:20081008T130831Z
SEQUENCE:0
END:VEVENT
END:VCALENDAR

this is my event and DTSTAMP is set. But when i try to retrieve events from calendar i always get the whole list and not only events in a specified time range.
Anyone here has caldav4j experience?