[Tickets #9726] Issues when synchronizing repeated events spanning DST change date

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Ticket URL: http://bugs.horde.org/ticket/9726
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  Ticket             | 9726
  Created By         | Nikolaus at rath.org
  Summary            | Issues when synchronizing repeated events spanning DST
                     | change date
  Queue              | Synchronization
  Version            | FRAMEWORK_3
  Type               | Bug
  State              | Unconfirmed
  Priority           | 1. Low
  Milestone          |
  Patch              |
  Owners             |
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Nikolaus at rath.org (2011-03-27 22:17) wrote:

Here is an example of a repeated event as it is send out by Horde when  
synchonizing over SyncML (set to repeat on Monday, 8pm from Feb 28th  
to May, 3rd):

                 BEGIN:VCALENDAR
                 VERSION:2.0
                 X-WR-CALNAME:gerti's Calendar
                 PRODID:-//The Horde Project//Horde_iCalendar  
Library\, Horde 3.3.8//EN
                 METHOD:PUBLISH
                 BEGIN:VEVENT
                 DTSTART:20110301T010000Z
                 DTEND:20110301T020000Z
                 DTSTAMP:20110327T142133Z
                 CREATED:20110327T142029Z
                 LAST-MODIFIED:20110327T142029Z
                 SUMMARY:Repeating One
                 ORGANIZER;CN=gerti:mailto:gerti
                 CLASS:PUBLIC
                 STATUS:CONFIRMED
                 TRANSP:OPAQUE
                 RRULE:FREQ=WEEKLY;INTERVAL=1;BYDAY=MO;UNTIL=20110505T035959Z
                 EXDATE:20110328T000000Z
                 EXDATE:20110328T000000Z
                 END:VEVENT
                 END:VCALENDAR

The Synthesis Android SyncML client is not able to handle this. Upon  
reporting this as a bug there, I was told that the problem is with  
horde. Specifically,

1) The Horde server is sending VCALENDAR 2.0 format, though it does  
not offer this format. The Synthesis client is accepting this (because  
it's clear what the server is intending to do), but it's not really  
according the SyncML standard. The Horde server should offer VCALENDAR  
2.0.

2) The Horde server is sending it as UTC without any timezone information.
That works for single events, but not for repeating events over the  
DST change date.
The Android client stores it locally in UTC timezone (without any DST rule).
The Horde server should send the VCALENDAR information for the given timezone.

3) The event is on Tuesday according to the given information, not on  
Monday (as written in the RRULE)
It would be Monday in the local time zone, but no such information is sent.

4) The Horde server is not sending a UID, that's why the Synthesis  
client will add one and send it
back with the next sync. That's why the client sends back even without  
any changes.

5) For sending back the Horde server does not allow UTC (and only  
VCALENDAR 1.0), that's why the Synthesis is sending back the events in  
floating format as VCALENDAR 1.0 which has several limitations for  
EXDATES.

6) The Horde server is sending two times the same EXDATE which is not correct.
This has no negative effect on client's side, but it's not ok that way.


Let me know if there is anything I can do to help getting this  
resolved. Tested Horde version is 3.3.8, kronolith 2.3.4.