Hi David,

great thanks a lot this solved the time shift problem. 
I did not had time to play with the different parameters. For now I simply added all of them.
I guess it has to do either with the timezone or with the daylight settings.
Maybe you want to add this to a "How-to install for SOGo" as a workaround.

One problem remain. If I change something in the caldav calendar, the time information in org get lost completely.
E.g.
* Meeting <2013-01-16 Wed 14:00>
becomes
* Meeting
It subsitutes the right entry and hence I believe it gets the ID stuff right. However, it seems to have trouble to interpret the time information right (and ignore them?).
If there is a way to help you debugging this please let me know.

Thanks again a lot


Torsten


(setq org-caldav-calendar-preamble
  "BEGIN:VCALENDAR
PRODID:-//Inverse inc./SOGo 2.0.3a//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Europe/Berlin
X-LIC-LOCATION:Europe/Berlin
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19700329T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19701025T030000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
END:VTIMEZONE
")

If it works for you with such a timezone definition, it'd be interesting
to know if SOGo needs all of that or if you could drop most of this
stuff.

-David