[horde] Horde 4.0.8: EXDATE problem

[Christian Schmidt]

Hi all,

we recently noticed a strange behaviour with or Horde 4.0.8
Installation:

Deleting single items from repeating appointments in kronolith results
in wrong EXDATE entries in the "corresponding" ICS Files.

Using kronolith, I created an event (April 9, 11:00am-12:00pm) which
repeats daily until April 12. Then I deleted the single appointment on
April 11. In kronolith, everything is fine, but after downloading the
calendar as ICS file, this shows a wrong EXDATE entry:

BEGIN:VEVENT
DTSTART:20130409T080000Z
DTEND:20130409T090000Z
DTSTAMP:20130408T164852Z
UID:<ZAPPED>
CREATED:20130408T164817Z
LAST-MODIFIED:20130408T164847Z
SUMMARY:Test-taeglich
CLASS:PUBLIC
STATUS:CONFIRMED
TRANSP:OPAQUE
RRULE:FREQ=DAILY;INTERVAL=1;UNTIL=20130412T215959Z
EXDATE:20130410T220000Z		<- Excludes April 10 and not 11!!
END:VEVENT

Trying with an event that repeats weekly, we get the same result with
an "off-by-1-day" value for EXDATE.

We're running
- Horde Groupware Webmail Edition 4.0.8
- Kronolith 3.0.17
on Debian 6 ("Squeeze").

Is this a bug in horde/kronolith or due to any (if so: which?) misconfiguration?

TIA!

Gruss/Regards,
Christian Schmidt

-- 
Your goose is cooked.
(Your current chick is burned up too!)