[Evolution] export from calendar does not work

["peter peter nameservice mobi" <peter peter nameservice mobi>]

Hi!
When I export evolution calendar on webdav-server,
evolution does only export calendar maybe for the next month, but not
for the next year:

BEGIN:VCALENDAR
CALSCALE:GREGORIAN
PRODID:-//Ximian//NONSGML Evolution Calendar//EN
VERSION:2.0
BEGIN:VFREEBUSY
ORGANIZER;CN=My Name
DTSTART:20080809T000000Z
DTEND:20080920T000000Z
FREEBUSY;FBTYPE=BUSY:20080810T160000Z/20080810T173000Z
[...]

Is it a bug?
A feature?
A setup problem?

What can I do, when evolution shell export calendar for the next year?

Gruss,
Peter