It works for me with Kolab backend, although the event info dialog displays "Repeat: Every 1 month(s), forever ". When I edit the event Recurrence form looks correct and the event is displayed properly on the 3rd Thursday as defined. So, I see only a problem with the "Repeat" text not being complete.

Is that what you're talking about? I believe Kolab backend is not using the Horde lib, so it might be that there's another bug there.

I think that the screen from the application will explain the problem better :)

Did attached screen help you repeat the error?

Any info? :) Is there anything I can help you to resolve this bug ?

Ok, I was testing a different case. However, this case also works with Kolab backend. I assume that you're using the database driver. Is it right?

Yes, it using plugins/calendar/drivers/database/database_driver.php.

The new_event method starts in database_driver and it starts _update_recurring. In this _update_recurring there is a calendar_recurrence object that creates Horde_Date_Recurrence on initialization where the problem is. :)

Currently, the calendar uses the database backend:

// backend type (database, kolab)

$ config ['calendar_driver'] = "database";

Is it possible to fix the problem on the "database" driver that the calendar is using?

This driver is not a high prio for us. Patches welcome.