diff --git a/plugins/libcalendaring/libcalendaring.php b/plugins/libcalendaring/libcalendaring.php
index 426f6f48..29f26171 100644
--- a/plugins/libcalendaring/libcalendaring.php
+++ b/plugins/libcalendaring/libcalendaring.php
@@ -1,1582 +1,1582 @@
 <?php
 
 /**
  * Library providing common functions for calendaring plugins
  *
  * Provides utility functions for calendar-related modules such as
  * - alarms display and dismissal
  * - attachment handling
  * - recurrence computation and UI elements
  * - ical parsing and exporting
  * - itip scheduling protocol
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 class libcalendaring extends rcube_plugin
 {
     public $rc;
     public $timezone;
     public $gmt_offset;
     public $dst_active;
     public $timezone_offset;
     public $ical_parts = array();
     public $ical_message;
 
     public $defaults = array(
         'calendar_date_format'  => "Y-m-d",
         'calendar_date_short'   => "M-j",
         'calendar_date_long'    => "F j Y",
         'calendar_date_agenda'  => "l M-d",
         'calendar_time_format'  => "H:m",
         'calendar_first_day'    => 1,
         'calendar_first_hour'   => 6,
         'calendar_date_format_sets' => array(
             'Y-m-d' => array('d M Y',   'm-d',  'l m-d'),
             'Y/m/d' => array('d M Y',   'm/d',  'l m/d'),
             'Y.m.d' => array('d M Y',   'm.d',  'l m.d'),
             'd-m-Y' => array('d M Y',   'd-m',  'l d-m'),
             'd/m/Y' => array('d M Y',   'd/m',  'l d/m'),
             'd.m.Y' => array('d M Y',  'd.m',  'l d.m'),
             'j.n.Y' => array('d M Y',  'd.m',  'l d.m'),
             'm/d/Y' => array('M d Y',   'm/d',  'l m/d'),
         ),
     );
 
     private static $instance;
 
     private $mail_ical_parser;
 
     /**
      * Singleton getter to allow direct access from other plugins
      */
     public static function get_instance()
     {
         if (!self::$instance) {
             self::$instance = new libcalendaring(rcube::get_instance()->plugins);
             self::$instance->init_instance();
         }
 
         return self::$instance;
     }
 
     /**
      * Initializes class properties
      */
     public function init_instance()
     {
         $this->rc = rcube::get_instance();
 
         // set user's timezone
         try {
             $this->timezone = new DateTimeZone($this->rc->config->get('timezone', 'GMT'));
         }
         catch (Exception $e) {
             $this->timezone = new DateTimeZone('GMT');
         }
 
         $now = new DateTime('now', $this->timezone);
 
         $this->gmt_offset      = $now->getOffset();
         $this->dst_active      = $now->format('I');
         $this->timezone_offset = $this->gmt_offset / 3600 - $this->dst_active;
 
         $this->add_texts('localization/', false);
     }
 
     /**
      * Required plugin startup method
      */
     public function init()
     {
         self::$instance = $this;
 
         $this->rc = rcube::get_instance();
         $this->init_instance();
 
         // include client scripts and styles
         if ($this->rc->output) {
             // add hook to display alarms
             $this->add_hook('refresh', array($this, 'refresh'));
             $this->register_action('plugin.alarms', array($this, 'alarms_action'));
             $this->register_action('plugin.expand_attendee_group', array($this, 'expand_attendee_group'));
         }
 
         // proceed initialization in startup hook
         $this->add_hook('startup', array($this, 'startup'));
     }
 
     /**
      * Startup hook
      */
     public function startup($args)
     {
         if ($this->rc->output && $this->rc->output->type == 'html') {
             $this->rc->output->set_env('libcal_settings', $this->load_settings());
             $this->include_script('libcalendaring.js');
             $this->include_stylesheet($this->local_skin_path() . '/libcal.css');
 
             $this->add_label(
                 'itipaccepted', 'itiptentative', 'itipdeclined',
                 'itipdelegated', 'expandattendeegroup', 'expandattendeegroupnodata',
                 'statusorganizer', 'statusaccepted', 'statusdeclined',
                 'statusdelegated', 'statusunknown', 'statusneeds-action',
                 'statustentative', 'statuscompleted', 'statusin-process',
                 'delegatedto', 'delegatedfrom', 'showmore'
             );
         }
 
         if ($args['task'] == 'mail') {
             if ($args['action'] == 'show' || $args['action'] == 'preview') {
                 $this->add_hook('message_load', array($this, 'mail_message_load'));
             }
         }
     }
 
     /**
      * Load iCalendar functions
      */
     public static function get_ical()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/libvcalendar.php';
         return new libvcalendar();
     }
 
     /**
      * Load iTip functions
      */
     public static function get_itip($domain = 'libcalendaring')
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_itip.php';
         return new libcalendaring_itip($self, $domain);
     }
 
     /**
      * Load recurrence computation engine
      */
     public static function get_recurrence()
     {
         $self = self::get_instance();
         require_once __DIR__ . '/lib/libcalendaring_recurrence.php';
         return new libcalendaring_recurrence($self);
     }
 
     /**
      * Shift dates into user's current timezone
      *
      * @param mixed Any kind of a date representation (DateTime object, string or unix timestamp)
      * @return object DateTime object in user's timezone
      */
     public function adjust_timezone($dt, $dateonly = false)
     {
         if (is_numeric($dt)) {
             $dt = new DateTime('@'.$dt);
         }
         else if (is_string($dt)) {
             $dt = rcube_utils::anytodatetime($dt);
         }
 
         if ($dt instanceof DateTime && empty($dt->_dateonly) && !$dateonly) {
             $dt->setTimezone($this->timezone);
         }
 
         return $dt;
     }
 
     /**
      *
      */
     public function load_settings()
     {
         $this->date_format_defaults();
 
         $settings = array();
         $keys     = array('date_format', 'time_format', 'date_short', 'date_long', 'date_agenda');
 
         foreach ($keys as $key) {
             $settings[$key] = (string)$this->rc->config->get('calendar_' . $key, $this->defaults['calendar_' . $key]);
             $settings[$key] = self::from_php_date_format($settings[$key]);
         }
 
         $settings['dates_long']  = $settings['date_long'];
         $settings['first_day']   = (int)$this->rc->config->get('calendar_first_day', $this->defaults['calendar_first_day']);
         $settings['timezone']    = $this->timezone_offset;
         $settings['dst']         = $this->dst_active;
 
         // localization
         $settings['days'] = array(
             $this->rc->gettext('sunday'),   $this->rc->gettext('monday'),
             $this->rc->gettext('tuesday'),  $this->rc->gettext('wednesday'),
             $this->rc->gettext('thursday'), $this->rc->gettext('friday'),
             $this->rc->gettext('saturday')
         );
         $settings['days_short'] = array(
             $this->rc->gettext('sun'), $this->rc->gettext('mon'),
             $this->rc->gettext('tue'), $this->rc->gettext('wed'),
             $this->rc->gettext('thu'), $this->rc->gettext('fri'),
             $this->rc->gettext('sat')
         );
         $settings['months'] = array(
             $this->rc->gettext('longjan'), $this->rc->gettext('longfeb'),
             $this->rc->gettext('longmar'), $this->rc->gettext('longapr'),
             $this->rc->gettext('longmay'), $this->rc->gettext('longjun'),
             $this->rc->gettext('longjul'), $this->rc->gettext('longaug'),
             $this->rc->gettext('longsep'), $this->rc->gettext('longoct'),
             $this->rc->gettext('longnov'), $this->rc->gettext('longdec')
         );
         $settings['months_short'] = array(
             $this->rc->gettext('jan'), $this->rc->gettext('feb'),
             $this->rc->gettext('mar'), $this->rc->gettext('apr'),
             $this->rc->gettext('may'), $this->rc->gettext('jun'),
             $this->rc->gettext('jul'), $this->rc->gettext('aug'),
             $this->rc->gettext('sep'), $this->rc->gettext('oct'),
             $this->rc->gettext('nov'), $this->rc->gettext('dec')
         );
         $settings['today'] = $this->rc->gettext('today');
 
         return $settings;
     }
 
 
     /**
      * Helper function to set date/time format according to config and user preferences
      */
     private function date_format_defaults()
     {
         static $defaults = array();
 
         // nothing to be done
         if (isset($defaults['date_format']))
           return;
 
         $defaults['date_format'] = $this->rc->config->get('calendar_date_format', $this->rc->config->get('date_format'));
         $defaults['time_format'] = $this->rc->config->get('calendar_time_format', $this->rc->config->get('time_format'));
 
         // override defaults
         if ($defaults['date_format'])
             $this->defaults['calendar_date_format'] = $defaults['date_format'];
         if ($defaults['time_format'])
             $this->defaults['calendar_time_format'] = $defaults['time_format'];
 
         // derive format variants from basic date format
         $format_sets = $this->rc->config->get('calendar_date_format_sets', $this->defaults['calendar_date_format_sets']);
         if ($format_set = $format_sets[$this->defaults['calendar_date_format']]) {
             $this->defaults['calendar_date_long'] = $format_set[0];
             $this->defaults['calendar_date_short'] = $format_set[1];
             $this->defaults['calendar_date_agenda'] = $format_set[2];
         }
     }
 
     /**
      * Compose a date string for the given event
      */
     public function event_date_text($event)
     {
         $fromto  = '--';
         $is_task = !empty($event['_type']) && $event['_type'] == 'task';
 
         $this->date_format_defaults();
 
         $date_format = self::to_php_date_format($this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']));
         $time_format = self::to_php_date_format($this->rc->config->get('calendar_time_format', $this->defaults['calendar_time_format']));
 
         $getTimezone = function ($date) {
             if ($newTz = $date->getTimezone()) {
                 return $newTz->getName();
             }
 
             return '';
         };
 
         $formatDate = function ($date, $format) use ($getTimezone) {
             // This is a workaround for the rcmail::format_date() which does not play nice with timezone
             $tz = $this->rc->config->get('timezone');
             if ($dateTz = $getTimezone($date)) {
                 $this->rc->config->set('timezone', $dateTz);
             }
             $result = $this->rc->format_date($date, $format);
             $this->rc->config->set('timezone', $tz);
 
             return $result;
         };
 
         // handle task objects
         if ($is_task && !empty($event['due']) && is_object($event['due'])) {
             $fromto = $formatDate($event['due'], !empty($event['due']->_dateonly) ? $date_format : null);
 
             // add timezone information
             if ($fromto && empty($event['due']->_dateonly) && ($tz = $getTimezone($event['due']))) {
                 $fromto .= ' (' . strtr($tz, '_', ' ') . ')';
             }
 
             return $fromto;
         }
 
         // abort if no valid event dates are given
         if (!is_object($event['start']) || !is_a($event['start'], 'DateTime') || !is_object($event['end']) || !is_a($event['end'], 'DateTime')) {
             return $fromto;
         }
 
         if ($event['allday']) {
             $fromto = $formatDate($event['start'], $date_format);
             if (($todate = $formatDate($event['end'], $date_format)) != $fromto) {
                 $fromto .= ' - ' . $todate;
             }
         }
         else if ($event['start']->format('Ymd') === $event['end']->format('Ymd')) {
             $fromto = $formatDate($event['start'], $date_format) . ' ' . $formatDate($event['start'], $time_format) .
                 ' - ' . $formatDate($event['end'], $time_format);
         }
         else {
             $fromto = $formatDate($event['start'], $date_format) . ' ' . $formatDate($event['start'], $time_format) .
                 ' - ' . $formatDate($event['end'], $date_format) . ' ' . $formatDate($event['end'], $time_format);
         }
 
         // add timezone information
         if ($fromto && empty($event['allday']) && ($tz = $getTimezone($event['start']))) {
             $fromto .= ' (' . strtr($tz, '_', ' ') . ')';
         }
 
         return $fromto;
     }
 
 
     /**
      * Render HTML form for alarm configuration
      */
     public function alarm_select($attrib, $alarm_types, $absolute_time = true)
     {
         unset($attrib['name']);
 
         $input_value    = new html_inputfield(array('name' => 'alarmvalue[]', 'class' => 'edit-alarm-value form-control', 'size' => 3));
         $input_date     = new html_inputfield(array('name' => 'alarmdate[]', 'class' => 'edit-alarm-date form-control', 'size' => 10));
         $input_time     = new html_inputfield(array('name' => 'alarmtime[]', 'class' => 'edit-alarm-time form-control', 'size' => 6));
         $select_type    = new html_select(array('name' => 'alarmtype[]', 'class' => 'edit-alarm-type form-control', 'id' => $attrib['id']));
         $select_offset  = new html_select(array('name' => 'alarmoffset[]', 'class' => 'edit-alarm-offset form-control'));
         $select_related = new html_select(array('name' => 'alarmrelated[]', 'class' => 'edit-alarm-related form-control'));
         $object_type    = !empty($attrib['_type']) ? $attrib['_type'] : 'event';
 
         $select_type->add($this->gettext('none'), '');
         foreach ($alarm_types as $type) {
             $select_type->add($this->gettext(strtolower("alarm{$type}option")), $type);
         }
 
         foreach (array('-M','-H','-D','+M','+H','+D') as $trigger) {
             $select_offset->add($this->gettext('trigger' . $trigger), $trigger);
         }
 
         $select_offset->add($this->gettext('trigger0'), '0');
         if ($absolute_time) {
             $select_offset->add($this->gettext('trigger@'), '@');
         }
 
         $select_related->add($this->gettext('relatedstart'), 'start');
         $select_related->add($this->gettext('relatedend' . $object_type), 'end');
 
         // pre-set with default values from user settings
         $preset = self::parse_alarm_value($this->rc->config->get('calendar_default_alarm_offset', '-15M'));
         $hidden = array('style' => 'display:none');
 
         return html::span('edit-alarm-set',
             $select_type->show($this->rc->config->get('calendar_default_alarm_type', '')) . ' ' .
             html::span(array('class' => 'edit-alarm-values input-group', 'style' => 'display:none'),
                 $input_value->show($preset[0]) . ' ' .
                 $select_offset->show($preset[1]) . ' ' .
                 $select_related->show() . ' ' .
                 $input_date->show('', $hidden) . ' ' .
                 $input_time->show('', $hidden)
             )
         );
     }
 
     /**
      * Get a list of email addresses of the given user (from login and identities)
      *
      * @param string User Email (default to current user)
      *
      * @return array Email addresses related to the user
      */
     public function get_user_emails($user = null)
     {
         static $_emails = array();
 
         if (empty($user)) {
             $user = $this->rc->user->get_username();
         }
 
         // return cached result
         if (isset($_emails[$user])) {
             return $_emails[$user];
         }
 
         $emails = array($user);
         $plugin = $this->rc->plugins->exec_hook('calendar_user_emails', array('emails' => $emails));
         $emails = array_map('strtolower', $plugin['emails']);
 
         // add all emails from the current user's identities
         if (!$plugin['abort'] && ($user == $this->rc->user->get_username())) {
             foreach ($this->rc->user->list_emails() as $identity) {
                 $emails[] = strtolower($identity['email']);
             }
         }
 
         $_emails[$user] = array_unique($emails);
         return $_emails[$user];
     }
 
     /**
      * Set the given participant status to the attendee matching the current user's identities
      * Unsets 'rsvp' flag too.
      *
      * @param array  &$event    Event data
      * @param string $status    The PARTSTAT value to set
      * @param bool   $recursive Recurive call
      *
      * @return mixed Email address of the updated attendee or False if none matching found
      */
     public function set_partstat(&$event, $status, $recursive = true)
     {
         $success = false;
         $emails = $this->get_user_emails();
         foreach ((array)$event['attendees'] as $i => $attendee) {
             if ($attendee['email'] && in_array(strtolower($attendee['email']), $emails)) {
                 $event['attendees'][$i]['status'] = strtoupper($status);
                 unset($event['attendees'][$i]['rsvp']);
                 $success = $attendee['email'];
             }
         }
 
         // apply partstat update to each existing exception
         if ($event['recurrence'] && is_array($event['recurrence']['EXCEPTIONS'])) {
             foreach ($event['recurrence']['EXCEPTIONS'] as $i => $exception) {
                 $this->set_partstat($event['recurrence']['EXCEPTIONS'][$i], $status, false);
             }
 
             // set link to top-level exceptions
             $event['exceptions'] = &$event['recurrence']['EXCEPTIONS'];
         }
 
         return $success;
     }
 
 
     /*********  Alarms handling  *********/
 
     /**
      * Helper function to convert alarm trigger strings
      * into two-field values (e.g. "-45M" => 45, "-M")
      */
     public static function parse_alarm_value($val)
     {
         if ($val[0] == '@') {
             return array(new DateTime($val));
         }
         else if (preg_match('/([+-]?)P?(T?\d+[HMSDW])+/', $val, $m) && preg_match_all('/T?(\d+)([HMSDW])/', $val, $m2, PREG_SET_ORDER)) {
             if ($m[1] == '')
                 $m[1] = '+';
             foreach ($m2 as $seg) {
                 $prefix = $seg[2] == 'D' || $seg[2] == 'W' ? 'P' : 'PT';
                 if ($seg[1] > 0) {  // ignore zero values
                     // convert seconds to minutes
                     if ($seg[2] == 'S') {
                         $seg[2] = 'M';
                         $seg[1] = max(1, round($seg[1]/60));
                     }
 
                     return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
                 }
             }
 
             // return zero value nevertheless
             return array($seg[1], $m[1].$seg[2], $m[1].$seg[1].$seg[2], $m[1].$prefix.$seg[1].$seg[2]);
         }
 
         return false;
     }
 
     /**
      * Convert the alarms list items to be processed on the client
      */
     public static function to_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'] instanceof DateTime) {
                 $alarm['trigger'] = '@' . $alarm['trigger']->format('U');
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[2];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public static function from_client_alarms($valarms)
     {
         return array_map(function($alarm){
             if ($alarm['trigger'][0] == '@') {
                 try {
                     $alarm['trigger'] = new DateTime($alarm['trigger']);
                     $alarm['trigger']->setTimezone(new DateTimeZone('UTC'));
                 }
                 catch (Exception $e) { /* handle this ? */ }
             }
             else if ($trigger = libcalendaring::parse_alarm_value($alarm['trigger'])) {
                 $alarm['trigger'] = $trigger[3];
             }
             return $alarm;
         }, (array)$valarms);
     }
 
     /**
      * Render localized text for alarm settings
      */
     public static function alarms_text($alarms)
     {
         if (is_array($alarms) && is_array($alarms[0])) {
             $texts = array();
             foreach ($alarms as $alarm) {
                 if ($text = self::alarm_text($alarm))
                     $texts[] = $text;
             }
 
             return join(', ', $texts);
         }
         else {
             return self::alarm_text($alarms);
         }
     }
 
     /**
      * Render localized text for a single alarm property
      */
     public static function alarm_text($alarm)
     {
         $related = null;
 
         if (is_string($alarm)) {
             list($trigger, $action) = explode(':', $alarm);
         }
         else {
             $trigger = $alarm['trigger'];
             $action  = $alarm['action'];
 
             if (!empty($alarm['related'])) {
                 $related = $alarm['related'];
             }
         }
 
         $text  = '';
         $rcube = rcube::get_instance();
 
         switch ($action) {
         case 'EMAIL':
             $text = $rcube->gettext('libcalendaring.alarmemail');
             break;
         case 'DISPLAY':
             $text = $rcube->gettext('libcalendaring.alarmdisplay');
             break;
         case 'AUDIO':
             $text = $rcube->gettext('libcalendaring.alarmaudio');
             break;
         }
 
         if ($trigger instanceof DateTime) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($trigger))
             ));
         }
         else if (preg_match('/@(\d+)/', $trigger, $m)) {
             $text .= ' ' . $rcube->gettext(array(
                 'name' => 'libcalendaring.alarmat',
                 'vars' => array('datetime' => $rcube->format_date($m[1]))
             ));
         }
         else if ($val = self::parse_alarm_value($trigger)) {
-            $r = strtoupper($related ?: 'start') == 'END' ? 'end' : '';
+            $r = $related && strtoupper($related) == 'END' ? 'end' : '';
             // TODO: for all-day events say 'on date of event at XX' ?
             if ($val[0] == 0) {
                 $text .= ' ' . $rcube->gettext('libcalendaring.triggerattime' . $r);
             }
             else {
                 $label = 'libcalendaring.trigger' . $r . $val[1];
                 $text .= ' ' . intval($val[0]) . ' ' . $rcube->gettext($label);
             }
         }
         else {
             return false;
         }
 
         return $text;
     }
 
     /**
      * Get the next alarm (time & action) for the given event
      *
      * @param array Record data
      * @return array Hash array with alarm time/type or null if no alarms are configured
      */
     public static function get_next_alarm($rec, $type = 'event')
     {
         if (
             (empty($rec['valarms']) && empty($rec['alarms']))
             || !empty($rec['cancelled'])
             || (!empty($rec['status']) && $rec['status'] == 'CANCELLED')
         ) {
             return null;
         }
 
         if ($type == 'task') {
             $timezone = self::get_instance()->timezone;
             if (!empty($rec['startdate'])) {
                 $time = !empty($rec['starttime']) ? $rec['starttime'] : '12:00';
                 $rec['start'] = new DateTime($rec['startdate'] . ' ' . $time, $timezone);
             }
             if (!empty($rec['date'])) {
                 $time = !empty($rec['time']) ? $rec['time'] : '12:00';
                 $rec[!empty($rec['start']) ? 'end' : 'start'] = new DateTime($rec['date'] . ' ' . $time, $timezone);
             }
         }
 
         if (empty($rec['end'])) {
             $rec['end'] = $rec['start'];
         }
 
         // support legacy format
         if (empty($rec['valarms'])) {
             list($trigger, $action) = explode(':', $rec['alarms'], 2);
             if ($alarm = self::parse_alarm_value($trigger)) {
                 $rec['valarms'] = array(array('action' => $action, 'trigger' => $alarm[3] ?: $alarm[0]));
             }
         }
 
         // alarm ID eq. record ID by default to keep backwards compatibility
         $alarm_id   = isset($rec['id']) ? $rec['id'] : null;
         $alarm_prop = null;
         $expires    = new DateTime('now - 12 hours');
         $notify_at  = null;
 
         // handle multiple alarms
         foreach ($rec['valarms'] as $alarm) {
             $notify_time = null;
 
             if ($alarm['trigger'] instanceof DateTime) {
                 $notify_time = $alarm['trigger'];
             }
             else if (is_string($alarm['trigger'])) {
                 $refdate = !empty($alarm['related']) && $alarm['related'] == 'END' ? $rec['end'] : $rec['start'];
 
                 // abort if no reference date is available to compute notification time
                 if (!is_a($refdate, 'DateTime')) {
                     continue;
                 }
 
                 // TODO: for all-day events, take start @ 00:00 as reference date ?
 
                 try {
                     $interval = new DateInterval(trim($alarm['trigger'], '+-'));
                     $interval->invert = $alarm['trigger'][0] == '-';
                     $notify_time = clone $refdate;
                     $notify_time->add($interval);
                 }
                 catch (Exception $e) {
                     rcube::raise_error($e, true);
                     continue;
                 }
             }
 
             if ($notify_time && (!$notify_at || ($notify_time > $notify_at && $notify_time > $expires))) {
                 $notify_at  = $notify_time;
                 $action     = isset($alarm['action']) ? $alarm['action'] : null;
                 $alarm_prop = $alarm;
 
                 // generate a unique alarm ID if multiple alarms are set
                 if (count($rec['valarms']) > 1) {
                     $rec_id = substr(md5(isset($rec['id']) ? $rec['id'] : 'none'), 0, 16);
                     $alarm_id = $rec_id . '-' . $notify_at->format('Ymd\THis');
                 }
             }
         }
 
         return !$notify_at ? null : array(
             'time'   => $notify_at->format('U'),
             'action' => !empty($action) ? strtoupper($action) : 'DISPLAY',
             'id'     => $alarm_id,
             'prop'   => $alarm_prop,
         );
     }
 
     /**
      * Handler for keep-alive requests
      * This will check for pending notifications and pass them to the client
      */
     public function refresh($attr)
     {
         // collect pending alarms from all providers (e.g. calendar, tasks)
         $plugin = $this->rc->plugins->exec_hook('pending_alarms', array(
             'time' => time(),
             'alarms' => array(),
         ));
 
         if (!$plugin['abort'] && !empty($plugin['alarms'])) {
             // make sure texts and env vars are available on client
             $this->add_texts('localization/', true);
             $this->rc->output->add_label('close');
             $this->rc->output->set_env('snooze_select', $this->snooze_select());
             $this->rc->output->command('plugin.display_alarms', $this->_alarms_output($plugin['alarms']));
         }
     }
 
     /**
      * Handler for alarm dismiss/snooze requests
      */
     public function alarms_action()
     {
 //        $action = rcube_utils::get_input_value('action', rcube_utils::INPUT_GPC);
         $data  = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
 
         $data['ids'] = explode(',', $data['id']);
         $plugin = $this->rc->plugins->exec_hook('dismiss_alarms', $data);
 
         if (!empty($plugin['success'])) {
             $this->rc->output->show_message('successfullysaved', 'confirmation');
         }
         else {
             $this->rc->output->show_message('calendar.errorsaving', 'error');
         }
     }
 
     /**
      * Generate reduced and streamlined output for pending alarms
      */
     private function _alarms_output($alarms)
     {
         $out = array();
         foreach ($alarms as $alarm) {
             $out[] = array(
                 'id'       => $alarm['id'],
                 'start'    => !empty($alarm['start']) ? $this->adjust_timezone($alarm['start'])->format('c') : '',
                 'end'      => !empty($alarm['end'])? $this->adjust_timezone($alarm['end'])->format('c') : '',
                 'allDay'   => !empty($alarm['allday']),
                 'action'   => $alarm['action'],
                 'title'    => $alarm['title'],
                 'location' => $alarm['location'],
                 'calendar' => $alarm['calendar'],
             );
         }
 
         return $out;
     }
 
     /**
      * Render a dropdown menu to choose snooze time
      */
     private function snooze_select($attrib = array())
     {
         $steps = array(
              5 => 'repeatinmin',
             10 => 'repeatinmin',
             15 => 'repeatinmin',
             20 => 'repeatinmin',
             30 => 'repeatinmin',
             60 => 'repeatinhr',
             120 => 'repeatinhrs',
             1440 => 'repeattomorrow',
             10080 => 'repeatinweek',
         );
 
         $items = array();
         foreach ($steps as $n => $label) {
             $items[] = html::tag('li', null, html::a(array('href' => "#" . ($n * 60), 'class' => 'active'),
                 $this->gettext(array('name' => $label, 'vars' => array('min' => $n % 60, 'hrs' => intval($n / 60))))));
         }
 
         return html::tag('ul', $attrib + array('class' => 'toolbarmenu menu'), join("\n", $items), html::$common_attrib);
     }
 
 
     /*********  Recurrence rules handling ********/
 
     /**
      * Render localized text describing the recurrence rule of an event
      */
     public function recurrence_text($rrule)
     {
         $limit     = 10;
         $exdates   = array();
         $format    = $this->rc->config->get('calendar_date_format', $this->defaults['calendar_date_format']);
         $format    = self::to_php_date_format($format);
         $format_fn = function($dt) use ($format) {
             return rcmail::get_instance()->format_date($dt, $format);
         };
 
         if (!empty($rrule['EXDATE']) && is_array($rrule['EXDATE'])) {
             $exdates = array_map($format_fn, $rrule['EXDATE']);
         }
 
         if (empty($rrule['FREQ']) && !empty($rrule['RDATE'])) {
             $rdates = array_map($format_fn, $rrule['RDATE']);
             $more   = false;
 
             if (!empty($exdates)) {
                 $rdates = array_diff($rdates, $exdates);
             }
 
             if (count($rdates) > $limit) {
                 $rdates = array_slice($rdates, 0, $limit);
                 $more   = true;
             }
 
             return $this->gettext('ondate') . ' ' . join(', ', $rdates) . ($more ? '...' : '');
         }
 
         $output  = sprintf('%s %d ', $this->gettext('every'), $rrule['INTERVAL'] ?: 1);
 
         switch ($rrule['FREQ']) {
         case 'DAILY':
             $output .= $this->gettext('days');
             break;
         case 'WEEKLY':
             $output .= $this->gettext('weeks');
             break;
         case 'MONTHLY':
             $output .= $this->gettext('months');
             break;
         case 'YEARLY':
             $output .= $this->gettext('years');
             break;
         }
 
         if (!empty($rrule['COUNT'])) {
             $until = $this->gettext(array('name' => 'forntimes', 'vars' => array('nr' => $rrule['COUNT'])));
         }
         else if (!empty($rrule['UNTIL'])) {
             $until = $this->gettext('recurrencend') . ' ' . $this->rc->format_date($rrule['UNTIL'], $format);
         }
         else {
             $until = $this->gettext('forever');
         }
 
         $output .= ', ' . $until;
 
         if (!empty($exdates)) {
             $more = false;
             if (count($exdates) > $limit) {
                 $exdates = array_slice($exdates, 0, $limit);
                 $more    = true;
             }
 
             $output  .= '; ' . $this->gettext('except') . ' ' . join(', ', $exdates) . ($more ? '...' : '');
         }
 
         return $output;
     }
 
     /**
      * Generate the form for recurrence settings
      */
     public function recurrence_form($attrib = array())
     {
         switch ($attrib['part']) {
             // frequency selector
             case 'frequency':
                 $select = new html_select(array('name' => 'frequency', 'id' => 'edit-recurrence-frequency', 'class' => 'form-control'));
                 $select->add($this->gettext('never'),   '');
                 $select->add($this->gettext('daily'),   'DAILY');
                 $select->add($this->gettext('weekly'),  'WEEKLY');
                 $select->add($this->gettext('monthly'), 'MONTHLY');
                 $select->add($this->gettext('yearly'),  'YEARLY');
                 $select->add($this->gettext('rdate'),   'RDATE');
                 $html = html::label(array('for' => 'edit-recurrence-frequency', 'class' => 'col-form-label col-sm-2'), $this->gettext('frequency'))
                     . html::div('col-sm-10', $select->show(''));
                 break;
 
             // daily recurrence
             case 'daily':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-daily'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-daily', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('days')))));
                 break;
 
             // weekly recurrence form
             case 'weekly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-weekly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-weekly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('weeks')))));
 
                 // weekday selection
                 $daymap   = array('sun','mon','tue','wed','thu','fri','sat');
                 $checkbox = new html_checkbox(array('name' => 'byday', 'class' => 'edit-recurrence-weekly-byday'));
                 $first    = $this->rc->config->get('calendar_first_day', 1);
 
                 for ($weekdays = '', $j = $first; $j <= $first+6; $j++) {
                     $d = $j % 7;
                     $weekdays .= html::label(array('class' => 'weekday'),
                         $checkbox->show('', array('value' => strtoupper(substr($daymap[$d], 0, 2)))) .
                         $this->gettext($daymap[$d])
                     ) . ' ';
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $weekdays));
                 break;
 
             // monthly recurrence form
             case 'monthly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-monthly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-monthly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('months')))));
 
                 $checkbox = new html_checkbox(array('name' => 'bymonthday', 'class' => 'edit-recurrence-monthly-bymonthday'));
                 for ($monthdays = '', $d = 1; $d <= 31; $d++) {
                     $monthdays .= html::label(array('class' => 'monthday'), $checkbox->show('', array('value' => $d)) . $d);
                     $monthdays .= $d % 7 ? ' ' : html::br();
                 }
 
                 // rule selectors
                 $radio = new html_radiobutton(array('name' => 'repeatmode', 'class' => 'edit-recurrence-monthly-mode'));
                 $table = new html_table(array('cols' => 2, 'border' => 0, 'cellpadding' => 0, 'class' => 'formtable'));
                 $table->add('label', html::label(null, $radio->show('BYMONTHDAY', array('value' => 'BYMONTHDAY')) . ' ' . $this->gettext('each')));
                 $table->add(null, $monthdays);
                 $table->add('label', html::label(null, $radio->show('', array('value' => 'BYDAY')) . ' ' . $this->gettext('every')));
                 $table->add('recurrence-onevery', $this->rrule_selectors($attrib['part']));
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bydays'))
                     . html::div('col-sm-10 form-control-plaintext', $table->show()));
                 break;
 
             // annually recurrence form
             case 'yearly':
                 $select = $this->interval_selector(array('name' => 'interval', 'class' => 'edit-recurrence-interval form-control', 'id' => 'edit-recurrence-interval-yearly'));
                 $html = html::div($attrib, html::label(array('for' => 'edit-recurrence-interval-yearly', 'class' => 'col-form-label col-sm-2'), $this->gettext('every'))
                     . html::div('col-sm-10 input-group', $select->show(1) . html::span('label-after input-group-append', html::span('input-group-text', $this->gettext('years')))));
 
                 // month selector
                 $monthmap = array('','jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec');
                 $checkbox = new html_checkbox(array('name' => 'bymonth', 'class' => 'edit-recurrence-yearly-bymonth'));
 
                 for ($months = '', $m = 1; $m <= 12; $m++) {
                     $months .= html::label(array('class' => 'month'), $checkbox->show(null, array('value' => $m)) . $this->gettext($monthmap[$m]));
                     $months .= $m % 4 ? ' ' : html::br();
                 }
 
                 $html .= html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), $this->gettext('bymonths'))
                     . html::div('col-sm-10 form-control-plaintext',
                         html::div(array('id' => 'edit-recurrence-yearly-bymonthblock'), $months)
                         . html::div('recurrence-onevery', $this->rrule_selectors($attrib['part'], '---'))
                     ));
                 break;
 
             // end of recurrence form
             case 'until':
                 $radio  = new html_radiobutton(array('name' => 'repeat', 'class' => 'edit-recurrence-until'));
                 $select = $this->interval_selector(array('name' => 'times', 'id' => 'edit-recurrence-repeat-times', 'class' => 'form-control'));
                 $input  = new html_inputfield(array('name' => 'untildate', 'id' => 'edit-recurrence-enddate', 'size' => '10', 'class' => 'form-control datepicker'));
 
                 $html = html::div('line first',
                     $radio->show('', array('value' => '', 'id' => 'edit-recurrence-repeat-forever'))
                         . ' ' . html::label('edit-recurrence-repeat-forever', $this->gettext('forever'))
                 );
 
                 $label = $this->gettext('ntimes');
                 if (strpos($label, '$') === 0) {
                     $label = str_replace('$n', '', $label);
                     $group  = $select->show(1)
                         . html::span('input-group-append', html::span('input-group-text', rcube::Q($label)));
                 }
                 else {
                     $label = str_replace('$n', '', $label);
                     $group  = html::span('input-group-prepend', html::span('input-group-text', rcube::Q($label)))
                         . $select->show(1);
                 }
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'count', 'id' => 'edit-recurrence-repeat-count'))
                         . ' ' . html::label('edit-recurrence-repeat-count', $this->gettext('for'))
                         . ' ' . html::span('input-group', $group)
                 );
 
                 $html .= html::div('line',
                     $radio->show('', array('value' => 'until', 'id' => 'edit-recurrence-repeat-until', 'aria-label' => $this->gettext('untilenddate')))
                         . ' ' . html::label('edit-recurrence-repeat-until', $this->gettext('untildate'))
                         . ' ' . $input->show('', array('aria-label' => $this->gettext('untilenddate')))
                 );
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2'), ucfirst($this->gettext('recurrencend')))
                     . html::div('col-sm-10', $html));
                 break;
 
             case 'rdate':
                 $ul     = html::tag('ul', array('id' => 'edit-recurrence-rdates', 'class' => 'recurrence-rdates'), '');
                 $input  = new html_inputfield(array('name' => 'rdate', 'id' => 'edit-recurrence-rdate-input', 'size' => "10", 'class' => 'form-control datepicker'));
                 $button = new html_inputfield(array('type' => 'button', 'class' => 'button add', 'value' => $this->gettext('addrdate')));
 
                 $html = html::div($attrib, html::label(array('class' => 'col-form-label col-sm-2', 'for' => 'edit-recurrence-rdate-input'), $this->gettext('bydates'))
                     . html::div('col-sm-10', $ul . html::div('inputform', $input->show() . $button->show())));
                 break;
         }
 
         return $html;
     }
 
     /**
      * Input field for interval selection
      */
     private function interval_selector($attrib)
     {
         $select = new html_select($attrib);
         $select->add(range(1,30), range(1,30));
         return $select;
     }
 
     /**
      * Drop-down menus for recurrence rules like "each last sunday of"
      */
     private function rrule_selectors($part, $noselect = null)
     {
         // rule selectors
         $select_prefix = new html_select(array('name' => 'bydayprefix', 'id' => "edit-recurrence-$part-prefix", 'class' => 'form-control'));
         if ($noselect) $select_prefix->add($noselect, '');
         $select_prefix->add(array(
                 $this->gettext('first'),
                 $this->gettext('second'),
                 $this->gettext('third'),
                 $this->gettext('fourth'),
                 $this->gettext('last')
             ),
             array(1, 2, 3, 4, -1));
 
         $select_wday = new html_select(array('name' => 'byday', 'id' => "edit-recurrence-$part-byday", 'class' => 'form-control'));
         if ($noselect) $select_wday->add($noselect, '');
 
         $daymap = array('sunday','monday','tuesday','wednesday','thursday','friday','saturday');
         $first = $this->rc->config->get('calendar_first_day', 1);
         for ($j = $first; $j <= $first+6; $j++) {
             $d = $j % 7;
             $select_wday->add($this->gettext($daymap[$d]), strtoupper(substr($daymap[$d], 0, 2)));
         }
 
         return $select_prefix->show() . '&nbsp;' . $select_wday->show();
     }
 
     /**
      * Convert the recurrence settings to be processed on the client
      */
     public function to_client_recurrence($recurrence, $allday = false)
     {
         if (!empty($recurrence['UNTIL'])) {
             $recurrence['UNTIL'] = $this->adjust_timezone($recurrence['UNTIL'], $allday)->format('c');
         }
 
         // format RDATE values
         if (!empty($recurrence['RDATE'])) {
             $libcal = $this;
             $recurrence['RDATE'] = array_map(function($rdate) use ($libcal) {
                 return $libcal->adjust_timezone($rdate, true)->format('c');
             }, (array) $recurrence['RDATE']);
         }
 
         unset($recurrence['EXCEPTIONS']);
 
         return $recurrence;
     }
 
     /**
      * Process the alarms values submitted by the client
      */
     public function from_client_recurrence($recurrence, $start = null)
     {
         if (is_array($recurrence) && !empty($recurrence['UNTIL'])) {
             $recurrence['UNTIL'] = new DateTime($recurrence['UNTIL'], $this->timezone);
         }
 
         if (is_array($recurrence) && !empty($recurrence['RDATE'])) {
             $tz = $this->timezone;
             $recurrence['RDATE'] = array_map(function($rdate) use ($tz, $start) {
                 try {
                     $dt = new DateTime($rdate, $tz);
                     if (is_a($start, 'DateTime'))
                         $dt->setTime($start->format('G'), $start->format('i'));
                     return $dt;
                 }
                 catch (Exception $e) {
                     return null;
                 }
             }, $recurrence['RDATE']);
         }
 
         return $recurrence;
     }
 
 
     /*********  iTip message detection  *********/
 
     /**
      * Check mail message structure of there are .ics files attached
      */
     public function mail_message_load($p)
     {
         $this->ical_message = $p['object'];
         $itip_part          = null;
 
         // check all message parts for .ics files
         foreach ((array)$this->ical_message->mime_parts as $part) {
             if (self::part_is_vcalendar($part, $this->ical_message)) {
                 if (!empty($part->ctype_parameters['method'])) {
                     $itip_part = $part->mime_id;
                 }
                 else {
                     $this->ical_parts[] = $part->mime_id;
                 }
             }
         }
 
         // priorize part with method parameter
         if ($itip_part) {
             $this->ical_parts = array($itip_part);
         }
     }
 
     /**
      * Getter for the parsed iCal objects attached to the current email message
      *
      * @return object libvcalendar parser instance with the parsed objects
      */
     public function get_mail_ical_objects()
     {
         // create parser and load ical objects
         if (!$this->mail_ical_parser) {
             $this->mail_ical_parser = $this->get_ical();
 
             foreach ($this->ical_parts as $mime_id) {
                 $part    = $this->ical_message->mime_parts[$mime_id];
                 $charset = $part->ctype_parameters['charset'] ?: RCUBE_CHARSET;
                 $this->mail_ical_parser->import($this->ical_message->get_part_body($mime_id, true), $charset);
 
                 // check if the parsed object is an instance of a recurring event/task
                 array_walk($this->mail_ical_parser->objects, 'libcalendaring::identify_recurrence_instance');
 
                 // stop on the part that has an iTip method specified
                 if (count($this->mail_ical_parser->objects) && $this->mail_ical_parser->method) {
                     $this->mail_ical_parser->message_date = $this->ical_message->headers->date;
                     $this->mail_ical_parser->mime_id = $mime_id;
 
                     // store the message's sender address for comparisons
                     $from = rcube_mime::decode_address_list($this->ical_message->headers->from, 1, true, null, true);
                     $this->mail_ical_parser->sender = !empty($from) ? $from[1] : '';
 
                     if (!empty($this->mail_ical_parser->sender)) {
                         foreach ($this->mail_ical_parser->objects as $i => $object) {
                             $this->mail_ical_parser->objects[$i]['_sender'] = $this->mail_ical_parser->sender;
                             $this->mail_ical_parser->objects[$i]['_sender_utf'] = rcube_utils::idn_to_utf8($this->mail_ical_parser->sender);
                         }
                     }
 
                     break;
                 }
             }
         }
 
         return $this->mail_ical_parser;
     }
 
     /**
      * Read the given mime message from IMAP and parse ical data
      *
      * @param string Mailbox name
      * @param string Message UID
      * @param string Message part ID and object index (e.g. '1.2:0')
      * @param string Object type filter (optional)
      *
      * @return array Hash array with the parsed iCal 
      */
     public function mail_get_itip_object($mbox, $uid, $mime_id, $type = null)
     {
         $charset = RCUBE_CHARSET;
 
         // establish imap connection
         $imap = $this->rc->get_storage();
         $imap->set_folder($mbox);
 
         if ($uid && $mime_id) {
             list($mime_id, $index) = explode(':', $mime_id);
 
             $part    = $imap->get_message_part($uid, $mime_id);
             $headers = $imap->get_message_headers($uid);
             $parser  = $this->get_ical();
 
             if (!empty($part->ctype_parameters['charset'])) {
                 $charset = $part->ctype_parameters['charset'];
             }
 
             if ($part) {
                 $objects = $parser->import($part, $charset);
             }
         }
 
         // successfully parsed events/tasks?
         if (!empty($objects) && ($object = $objects[$index]) && (!$type || $object['_type'] == $type)) {
             if ($parser->method)
                 $object['_method'] = $parser->method;
 
             // store the message's sender address for comparisons
             $from = rcube_mime::decode_address_list($headers->from, 1, true, null, true);
             $object['_sender'] = !empty($from) ? $from[1] : '';
             $object['_sender_utf'] = rcube_utils::idn_to_utf8($object['_sender']);
 
             // check if this is an instance of a recurring event/task
             self::identify_recurrence_instance($object);
 
             return $object;
         }
 
         return null;
     }
 
     /**
      * Checks if specified message part is a vcalendar data
      *
      * @param rcube_message_part Part object
      * @param rcube_message      Message object
      *
      * @return boolean True if part is of type vcard
      */
     public static function part_is_vcalendar($part, $message = null)
     {
         // First check if the message is "valid" (i.e. not multipart/report)
         if ($message) {
             $level = explode('.', $part->mime_id);
 
             while (array_pop($level) !== null) {
                 $id     = join('.', $level) ?: 0;
                 $parent = !empty($message->mime_parts[$id]) ? $message->mime_parts[$id] : null;
                 if ($parent && $parent->mimetype == 'multipart/report') {
                     return false;
                 }
             }
         }
 
         return (
             in_array($part->mimetype, array('text/calendar', 'text/x-vcalendar', 'application/ics')) ||
             // Apple sends files as application/x-any (!?)
             ($part->mimetype == 'application/x-any' && !empty($part->filename) && preg_match('/\.ics$/i', $part->filename))
         );
     }
 
     /**
      * Single occourrences of recurring events are identified by their RECURRENCE-ID property
      * in iCal which is represented as 'recurrence_date' in our internal data structure.
      *
      * Check if such a property exists and derive the '_instance' identifier and '_savemode'
      * attributes which are used in the storage backend to identify the nested exception item.
      */
     public static function identify_recurrence_instance(&$object)
     {
         // for savemode=all, remove recurrence instance identifiers
         if (!empty($object['_savemode']) && $object['_savemode'] == 'all' && $object['recurrence']) {
             unset($object['_instance'], $object['recurrence_date']);
         }
         // set instance and 'savemode' according to recurrence-id
         else if (!empty($object['recurrence_date']) && is_a($object['recurrence_date'], 'DateTime')) {
             $object['_instance'] = self::recurrence_instance_identifier($object);
             $object['_savemode'] = $object['thisandfuture'] ? 'future' : 'current';
         }
         else if (!empty($object['recurrence_id']) && !empty($object['_instance'])) {
             if (strlen($object['_instance']) > 4) {
                 $object['recurrence_date'] = rcube_utils::anytodatetime($object['_instance'], $object['start']->getTimezone());
             }
             else {
                 $object['recurrence_date'] = clone $object['start'];
             }
         }
     }
 
     /**
      * Return a date() format string to render identifiers for recurrence instances
      *
      * @param array Hash array with event properties
      * @return string Format string
      */
     public static function recurrence_id_format($event)
     {
         return !empty($event['allday']) ? 'Ymd' : 'Ymd\THis';
     }
 
     /**
      * Return the identifer for the given instance of a recurring event
      *
      * @param array Hash array with event properties
      * @param bool  All-day flag from the main event
      *
      * @return mixed Format string or null if identifier cannot be generated
      */
     public static function recurrence_instance_identifier($event, $allday = null)
     {
         $instance_date = !empty($event['recurrence_date']) ? $event['recurrence_date'] : $event['start'];
 
         if ($instance_date instanceof DateTime) {
             // According to RFC5545 (3.8.4.4) RECURRENCE-ID format should
             // be date/date-time depending on the main event type, not the exception
             if ($allday === null) {
                 $allday = !empty($event['allday']);
             }
 
             return $instance_date->format($allday ? 'Ymd' : 'Ymd\THis');
         }
     }
 
 
     /*********  Attendee handling functions  *********/
 
     /**
      * Handler for attendee group expansion requests
      */
     public function expand_attendee_group()
     {
         $id     = rcube_utils::get_input_value('id', rcube_utils::INPUT_POST);
         $data   = rcube_utils::get_input_value('data', rcube_utils::INPUT_POST, true);
         $result = array('id' => $id, 'members' => array());
         $maxnum = 500;
 
         // iterate over all autocomplete address books (we don't know the source of the group)
         foreach ((array)$this->rc->config->get('autocomplete_addressbooks', 'sql') as $abook_id) {
             if (($abook = $this->rc->get_address_book($abook_id)) && $abook->groups) {
                 foreach ($abook->list_groups($data['name'], 1) as $group) {
                     // this is the matching group to expand
                     if (in_array($data['email'], (array)$group['email'])) {
                         $abook->set_pagesize($maxnum);
                         $abook->set_group($group['ID']);
 
                         // get all members
                         $res = $abook->list_records($this->rc->config->get('contactlist_fields'));
 
                         // handle errors (e.g. sizelimit, timelimit)
                         if ($abook->get_error()) {
                             $result['error'] = $this->rc->gettext('expandattendeegrouperror', 'libcalendaring');
                             $res = false;
                         }
                         // check for maximum number of members (we don't wanna bloat the UI too much)
                         else if ($res->count > $maxnum) {
                             $result['error'] = $this->rc->gettext('expandattendeegroupsizelimit', 'libcalendaring');
                             $res = false;
                         }
 
                         while ($res && ($member = $res->iterate())) {
                             $emails = (array)$abook->get_col_values('email', $member, true);
                             if (!empty($emails) && ($email = array_shift($emails))) {
                                 $result['members'][] = array(
                                     'email' => $email,
                                     'name' => rcube_addressbook::compose_list_name($member),
                                 );
                             }
                         }
 
                         break 2;
                     }
                 }
             }
         }
 
         $this->rc->output->command('plugin.expand_attendee_callback', $result);
     }
 
     /**
      * Merge attendees of the old and new event version
      * with keeping current user and his delegatees status
      *
      * @param array &$new   New object data
      * @param array $old    Old object data
      * @param bool  $status New status of the current user
      */
     public function merge_attendees(&$new, $old, $status = null)
     {
         if (empty($status)) {
             $emails    = $this->get_user_emails();
             $delegates = array();
             $attendees = array();
 
             // keep attendee status of the current user
             foreach ((array) $new['attendees'] as $i => $attendee) {
                 if (empty($attendee['email'])) {
                     continue;
                 }
 
                 $attendees[] = $email = strtolower($attendee['email']);
 
                 if (in_array($email, $emails)) {
                     foreach ($old['attendees'] as $_attendee) {
                         if ($attendee['email'] == $_attendee['email']) {
                             $new['attendees'][$i] = $_attendee;
                             if ($_attendee['status'] == 'DELEGATED' && ($email = $_attendee['delegated-to'])) {
                                 $delegates[] = strtolower($email);
                             }
 
                             break;
                         }
                     }
                 }
             }
 
             // make sure delegated attendee is not lost
             foreach ($delegates as $delegatee) {
                 if (!in_array($delegatee, $attendees)) {
                     foreach ((array) $old['attendees'] as $attendee) {
                         if ($attendee['email'] && ($email = strtolower($attendee['email'])) && $email == $delegatee) {
                             $new['attendees'][] = $attendee;
                             break;
                         }
                     }
                 }
             }
         }
 
         // We also make sure that status of any attendee
         // is not overriden by NEEDS-ACTION if it was already set
         // which could happen if you work with shared events
         foreach ((array) $new['attendees'] as $i => $attendee) {
             if ($attendee['email'] && $attendee['status'] == 'NEEDS-ACTION') {
                 foreach ($old['attendees'] as $_attendee) {
                     if ($attendee['email'] == $_attendee['email']) {
                         $new['attendees'][$i]['status'] = $_attendee['status'];
                         unset($new['attendees'][$i]['rsvp']);
                         break;
                     }
                 }
             }
         }
     }
 
 
     /*********  Static utility functions  *********/
 
     /**
      * Convert the internal structured data into a vcalendar rrule 2.0 string
      */
     public static function to_rrule($recurrence, $allday = false)
     {
         if (is_string($recurrence)) {
             return $recurrence;
         }
 
         $rrule = '';
         foreach ((array)$recurrence as $k => $val) {
             $k = strtoupper($k);
             switch ($k) {
             case 'UNTIL':
                 // convert to UTC according to RFC 5545
                 if (is_a($val, 'DateTime')) {
                     if (!$allday && empty($val->_dateonly)) {
                         $until = clone $val;
                         $until->setTimezone(new DateTimeZone('UTC'));
                         $val = $until->format('Ymd\THis\Z');
                     }
                     else {
                         $val = $val->format('Ymd');
                     }
                 }
                 break;
             case 'RDATE':
             case 'EXDATE':
                 foreach ((array)$val as $i => $ex) {
                     if (is_a($ex, 'DateTime')) {
                         $val[$i] = $ex->format('Ymd\THis');
                     }
                 }
                 $val = join(',', (array)$val);
                 break;
             case 'EXCEPTIONS':
                 continue 2;
             }
 
             if (strlen($val)) {
                 $rrule .= $k . '=' . $val . ';';
             }
         }
 
         return rtrim($rrule, ';');
     }
 
     /**
      * Convert from fullcalendar date format to PHP date() format string
      */
     public static function to_php_date_format($from)
     {
         // "dd.MM.yyyy HH:mm:ss" => "d.m.Y H:i:s"
         return strtr(strtr($from, array(
             'YYYY' => 'Y',
             'YY'   => 'y',
             'yyyy' => 'Y',
             'yy'   => 'y',
             'MMMM' => 'F',
             'MMM'  => 'M',
             'MM'   => 'm',
             'M'    => 'n',
             'dddd' => 'l',
             'ddd'  => 'D',
             'DD'   => 'd',
             'D'    => 'j',
             'HH'   => '**',
             'hh'   => '%%',
             'H'    => 'G',
             'h'    => 'g',
             'mm'   => 'i',
             'ss'   => 's',
             'TT'   => 'A',
             'tt'   => 'a',
             'T'    => 'A',
             't'    => 'a',
             'u'    => 'c',
         )), array(
             '**'   => 'H',
             '%%'   => 'h',
         ));
     }
 
     /**
      * Convert from PHP date() format to fullcalendar (MomentJS) format string
      */
     public static function from_php_date_format($from)
     {
         // "d.m.Y H:i:s" => "dd.MM.yyyy HH:mm:ss"
         return strtr($from, array(
             'y' => 'YY',
             'Y' => 'YYYY',
             'M' => 'MMM',
             'F' => 'MMMM',
             'm' => 'MM',
             'n' => 'M',
             'j' => 'D',
             'd' => 'DD',
             'D' => 'ddd',
             'l' => 'dddd',
             'H' => 'HH',
             'h' => 'hh',
             'G' => 'H',
             'g' => 'h',
             'i' => 'mm',
             's' => 'ss',
             'c' => '',
         ));
     }
 }
diff --git a/plugins/libkolab/lib/kolab_format_xcal.php b/plugins/libkolab/lib/kolab_format_xcal.php
index 96e0a740..9168e63f 100644
--- a/plugins/libkolab/lib/kolab_format_xcal.php
+++ b/plugins/libkolab/lib/kolab_format_xcal.php
@@ -1,779 +1,779 @@
 <?php
 
 /**
  * Xcal based Kolab format class wrapping libkolabxml bindings
  *
  * Base class for xcal-based Kolab groupware objects such as event, todo, journal
  *
  * @version @package_version@
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2012, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 abstract class kolab_format_xcal extends kolab_format
 {
     public $CTYPE = 'application/calendar+xml';
 
     public static $fulltext_cols = array('title', 'description', 'location', 'attendees:name', 'attendees:email', 'categories');
 
     public static $scheduling_properties = array('start', 'end', 'location');
 
     protected $_scheduling_properties = null;
 
     protected $sensitivity_map = array(
         'public'       => kolabformat::ClassPublic,
         'private'      => kolabformat::ClassPrivate,
         'confidential' => kolabformat::ClassConfidential,
     );
 
     protected $role_map = array(
         'REQ-PARTICIPANT' => kolabformat::Required,
         'OPT-PARTICIPANT' => kolabformat::Optional,
         'NON-PARTICIPANT' => kolabformat::NonParticipant,
         'CHAIR' => kolabformat::Chair,
     );
 
     protected $cutype_map = array(
         'INDIVIDUAL' => kolabformat::CutypeIndividual,
         'GROUP'      => kolabformat::CutypeGroup,
         'ROOM'       => kolabformat::CutypeRoom,
         'RESOURCE'   => kolabformat::CutypeResource,
         'UNKNOWN'    => kolabformat::CutypeUnknown,
     );
 
     protected $rrule_type_map = array(
         'MINUTELY' => RecurrenceRule::Minutely,
         'HOURLY' => RecurrenceRule::Hourly,
         'DAILY' => RecurrenceRule::Daily,
         'WEEKLY' => RecurrenceRule::Weekly,
         'MONTHLY' => RecurrenceRule::Monthly,
         'YEARLY' => RecurrenceRule::Yearly,
     );
 
     protected $weekday_map = array(
         'MO' => kolabformat::Monday,
         'TU' => kolabformat::Tuesday,
         'WE' => kolabformat::Wednesday,
         'TH' => kolabformat::Thursday,
         'FR' => kolabformat::Friday,
         'SA' => kolabformat::Saturday,
         'SU' => kolabformat::Sunday,
     );
 
     protected $alarm_type_map = array(
         'DISPLAY' => Alarm::DisplayAlarm,
         'EMAIL' => Alarm::EMailAlarm,
         'AUDIO' => Alarm::AudioAlarm,
     );
 
     protected $status_map = array(
         'NEEDS-ACTION' => kolabformat::StatusNeedsAction,
         'IN-PROCESS'   => kolabformat::StatusInProcess,
         'COMPLETED'    => kolabformat::StatusCompleted,
         'CANCELLED'    => kolabformat::StatusCancelled,
         'TENTATIVE'    => kolabformat::StatusTentative,
         'CONFIRMED'    => kolabformat::StatusConfirmed,
         'DRAFT'        => kolabformat::StatusDraft,
         'FINAL'        => kolabformat::StatusFinal,
     );
 
     protected $part_status_map = array(
         'UNKNOWN'      => kolabformat::PartNeedsAction,
         'NEEDS-ACTION' => kolabformat::PartNeedsAction,
         'TENTATIVE'    => kolabformat::PartTentative,
         'ACCEPTED'     => kolabformat::PartAccepted,
         'DECLINED'     => kolabformat::PartDeclined,
         'DELEGATED'    => kolabformat::PartDelegated,
         'IN-PROCESS'   => kolabformat::PartInProcess,
         'COMPLETED'    => kolabformat::PartCompleted,
       );
 
 
     /**
      * Convert common xcard properties into a hash array data structure
      *
      * @param array Additional data for merge
      *
      * @return array  Object data as hash array
      */
     public function to_array($data = array())
     {
         // read common object props
         $object = parent::to_array($data);
 
         $status_map = array_flip($this->status_map);
         $sensitivity_map = array_flip($this->sensitivity_map);
 
         $object += array(
             'sequence'    => intval($this->obj->sequence()),
             'title'       => $this->obj->summary(),
             'location'    => $this->obj->location(),
             'description' => $this->obj->description(),
             'url'         => $this->obj->url(),
             'status'      => $status_map[$this->obj->status()],
             'sensitivity' => $sensitivity_map[$this->obj->classification()],
             'priority'    => $this->obj->priority(),
             'categories'  => self::vector2array($this->obj->categories()),
             'start'       => self::php_datetime($this->obj->start()),
         );
 
         if (method_exists($this->obj, 'comment')) {
             $object['comment'] = $this->obj->comment();
         }
 
         // read organizer and attendees
         if (($organizer = $this->obj->organizer()) && ($organizer->email() || $organizer->name())) {
             $object['organizer'] = array(
                 'email' => $organizer->email(),
                 'name' => $organizer->name(),
             );
         }
 
         $role_map = array_flip($this->role_map);
         $cutype_map = array_flip($this->cutype_map);
         $part_status_map = array_flip($this->part_status_map);
         $attvec = $this->obj->attendees();
         for ($i=0; $i < $attvec->size(); $i++) {
             $attendee = $attvec->get($i);
             $cr = $attendee->contact();
             if ($cr->email() != $object['organizer']['email']) {
                 $delegators = $delegatees = array();
                 $vdelegators = $attendee->delegatedFrom();
                 for ($j=0; $j < $vdelegators->size(); $j++) {
                     $delegators[] = $vdelegators->get($j)->email();
                 }
                 $vdelegatees = $attendee->delegatedTo();
                 for ($j=0; $j < $vdelegatees->size(); $j++) {
                     $delegatees[] = $vdelegatees->get($j)->email();
                 }
 
                 $object['attendees'][] = array(
                     'role' => $role_map[$attendee->role()],
                     'cutype' => $cutype_map[$attendee->cutype()],
                     'status' => $part_status_map[$attendee->partStat()],
                     'rsvp' => $attendee->rsvp(),
                     'email' => $cr->email(),
                     'name' => $cr->name(),
                     'delegated-from' => $delegators,
                     'delegated-to' => $delegatees,
                 );
             }
         }
 
         if ($object['start'] instanceof DateTime) {
             $start_tz = $object['start']->getTimezone();
         }
 
         // read recurrence rule
         if (($rr = $this->obj->recurrenceRule()) && $rr->isValid()) {
             $rrule_type_map = array_flip($this->rrule_type_map);
             $object['recurrence'] = array('FREQ' => $rrule_type_map[$rr->frequency()]);
 
             if ($intvl = $rr->interval())
                 $object['recurrence']['INTERVAL'] = $intvl;
 
             if (($count = $rr->count()) && $count > 0) {
                 $object['recurrence']['COUNT'] = $count;
             }
             else if ($until = self::php_datetime($rr->end(), $start_tz)) {
                 $refdate = $this->get_reference_date();
                 if ($refdate && $refdate instanceof DateTime && !$refdate->_dateonly) {
                     $until->setTime($refdate->format('G'), $refdate->format('i'), 0);
                 }
                 $object['recurrence']['UNTIL'] = $until;
             }
 
             if (($byday = $rr->byday()) && $byday->size()) {
                 $weekday_map = array_flip($this->weekday_map);
                 $weekdays = array();
                 for ($i=0; $i < $byday->size(); $i++) {
                     $daypos = $byday->get($i);
                     $prefix = $daypos->occurence();
                     $weekdays[] = ($prefix ?: '') . $weekday_map[$daypos->weekday()];
                 }
                 $object['recurrence']['BYDAY'] = join(',', $weekdays);
             }
 
             if (($bymday = $rr->bymonthday()) && $bymday->size()) {
                 $object['recurrence']['BYMONTHDAY'] = join(',', self::vector2array($bymday));
             }
 
             if (($bymonth = $rr->bymonth()) && $bymonth->size()) {
                 $object['recurrence']['BYMONTH'] = join(',', self::vector2array($bymonth));
             }
 
             if ($exdates = $this->obj->exceptionDates()) {
                 for ($i=0; $i < $exdates->size(); $i++) {
                     if ($exdate = self::php_datetime($exdates->get($i), $start_tz)) {
                         $object['recurrence']['EXDATE'][] = $exdate;
                     }
                 }
             }
         }
 
         if ($rdates = $this->obj->recurrenceDates()) {
             for ($i=0; $i < $rdates->size(); $i++) {
                 if ($rdate = self::php_datetime($rdates->get($i), $start_tz)) {
                     $object['recurrence']['RDATE'][] = $rdate;
                 }
             }
         }
 
         // read alarm
         $valarms = $this->obj->alarms();
         $alarm_types = array_flip($this->alarm_type_map);
         $object['valarms'] = array();
         for ($i=0; $i < $valarms->size(); $i++) {
             $alarm = $valarms->get($i);
             $type  = $alarm_types[$alarm->type()];
 
             if ($type == 'DISPLAY' || $type == 'EMAIL' || $type == 'AUDIO') {  // only some alarms are supported
                 $valarm = array(
                     'action'      => $type,
                     'summary'     => $alarm->summary(),
                     'description' => $alarm->description(),
                 );
 
                 if ($type == 'EMAIL') {
                     $valarm['attendees'] = array();
                     $attvec = $alarm->attendees();
                     for ($j=0; $j < $attvec->size(); $j++) {
                         $cr = $attvec->get($j);
                         $valarm['attendees'][] = $cr->email();
                     }
                 }
                 else if ($type == 'AUDIO') {
                     $attach = $alarm->audioFile();
                     $valarm['uri'] = $attach->uri();
                 }
 
                 if ($start = self::php_datetime($alarm->start())) {
                     $object['alarms']  = '@' . $start->format('U');
                     $valarm['trigger'] = $start;
                 }
                 else if ($offset = $alarm->relativeStart()) {
                     $prefix = $offset->isNegative() ? '-' : '+';
                     $value  = '';
                     $time   = '';
 
                     if      ($w = $offset->weeks())     $value .= $w . 'W';
                     else if ($d = $offset->days())      $value .= $d . 'D';
                     else if ($h = $offset->hours())     $time  .= $h . 'H';
                     else if ($m = $offset->minutes())   $time  .= $m . 'M';
                     else if ($s = $offset->seconds())   $time  .= $s . 'S';
 
                     // assume 'at event time'
                     if (empty($value) && empty($time)) {
                         $prefix = '';
                         $time   = '0S';
                     }
 
                     $object['alarms']  = $prefix . $value . $time;
                     $valarm['trigger'] = $prefix . 'P' . $value . ($time ? 'T' . $time : '');
 
                     if ($alarm->relativeTo() == kolabformat::End) {
-                        $valarm['related'] == 'END';
+                        $valarm['related'] = 'END';
                     }
                 }
 
                 // read alarm duration and repeat properties
                 if (($duration = $alarm->duration()) && $duration->isValid()) {
                     $value = $time = '';
 
                     if      ($w = $duration->weeks())     $value .= $w . 'W';
                     else if ($d = $duration->days())      $value .= $d . 'D';
                     else if ($h = $duration->hours())     $time  .= $h . 'H';
                     else if ($m = $duration->minutes())   $time  .= $m . 'M';
                     else if ($s = $duration->seconds())   $time  .= $s . 'S';
 
                     $valarm['duration'] = 'P' . $value . ($time ? 'T' . $time : '');
                     $valarm['repeat']   = $alarm->numrepeat();
                 }
 
                 $object['alarms']  .= ':' . $type;  // legacy property
                 $object['valarms'][] = array_filter($valarm);
             }
         }
 
         $this->get_attachments($object);
 
         return $object;
     }
 
 
     /**
      * Set common xcal properties to the kolabformat object
      *
      * @param array  Event data as hash array
      */
     public function set(&$object)
     {
         $this->init();
 
         $is_new = !$this->obj->uid();
         $old_sequence = $this->obj->sequence();
         $reschedule = $is_new;
 
         // set common object properties
         parent::set($object);
 
         // set sequence value
         if (!isset($object['sequence'])) {
             if ($is_new) {
                 $object['sequence'] = 0;
             }
             else {
                 $object['sequence'] = $old_sequence;
 
                 // increment sequence when updating properties relevant for scheduling.
                 // RFC 5545: "It is incremented [...] each time the Organizer makes a significant revision to the calendar component."
                 if ($this->check_rescheduling($object)) {
                     $object['sequence']++;
                 }
             }
         }
         $this->obj->setSequence(intval($object['sequence']));
 
         if ($object['sequence'] > $old_sequence) {
             $reschedule = true;
         }
 
         $this->obj->setSummary($object['title']);
         $this->obj->setLocation($object['location']);
         $this->obj->setDescription($object['description']);
         $this->obj->setPriority($object['priority']);
         $this->obj->setClassification($this->sensitivity_map[$object['sensitivity']]);
         $this->obj->setCategories(self::array2vector($object['categories']));
         $this->obj->setUrl(strval($object['url']));
 
         if (method_exists($this->obj, 'setComment')) {
             $this->obj->setComment($object['comment']);
         }
 
         // process event attendees
         $attendees = new vectorattendee;
         foreach ((array)$object['attendees'] as $i => $attendee) {
             if ($attendee['role'] == 'ORGANIZER') {
                 $object['organizer'] = $attendee;
             }
             else if ($attendee['email'] != $object['organizer']['email']) {
                 $cr = new ContactReference(ContactReference::EmailReference, $attendee['email']);
                 $cr->setName($attendee['name']);
 
                 // set attendee RSVP if missing
                 if (!isset($attendee['rsvp'])) {
                     $object['attendees'][$i]['rsvp'] = $attendee['rsvp'] = $reschedule;
                 }
 
                 $att = new Attendee;
                 $att->setContact($cr);
                 $att->setPartStat($this->part_status_map[$attendee['status']]);
                 $att->setRole($this->role_map[$attendee['role']] ?: kolabformat::Required);
                 $att->setCutype($this->cutype_map[$attendee['cutype']] ?: kolabformat::CutypeIndividual);
                 $att->setRSVP((bool)$attendee['rsvp']);
 
                 if (!empty($attendee['delegated-from'])) {
                     $vdelegators = new vectorcontactref;
                     foreach ((array)$attendee['delegated-from'] as $delegator) {
                         $vdelegators->push(new ContactReference(ContactReference::EmailReference, $delegator));
                     }
                     $att->setDelegatedFrom($vdelegators);
                 }
                 if (!empty($attendee['delegated-to'])) {
                     $vdelegatees = new vectorcontactref;
                     foreach ((array)$attendee['delegated-to'] as $delegatee) {
                         $vdelegatees->push(new ContactReference(ContactReference::EmailReference, $delegatee));
                     }
                     $att->setDelegatedTo($vdelegatees);
                 }
 
                 if ($att->isValid()) {
                     $attendees->push($att);
                 }
                 else {
                     rcube::raise_error(array(
                         'code' => 600, 'type' => 'php',
                         'file' => __FILE__, 'line' => __LINE__,
                         'message' => "Invalid event attendee: " . json_encode($attendee),
                     ), true);
                 }
             }
         }
         $this->obj->setAttendees($attendees);
 
         if ($object['organizer']) {
             $organizer = new ContactReference(ContactReference::EmailReference, $object['organizer']['email']);
             $organizer->setName($object['organizer']['name']);
             $this->obj->setOrganizer($organizer);
         }
 
         if ($object['start'] instanceof DateTime) {
             $start_tz = $object['start']->getTimezone();
         }
 
         // save recurrence rule
         $rr = new RecurrenceRule;
         $rr->setFrequency(RecurrenceRule::FreqNone);
 
         if ($object['recurrence'] && !empty($object['recurrence']['FREQ'])) {
             $freq     = $object['recurrence']['FREQ'];
             $bysetpos = explode(',', $object['recurrence']['BYSETPOS']);
 
             $rr->setFrequency($this->rrule_type_map[$freq]);
 
             if ($object['recurrence']['INTERVAL'])
                 $rr->setInterval(intval($object['recurrence']['INTERVAL']));
 
             if ($object['recurrence']['BYDAY']) {
                 $byday = new vectordaypos;
                 foreach (explode(',', $object['recurrence']['BYDAY']) as $day) {
                     $occurrence = 0;
                     if (preg_match('/^([\d-]+)([A-Z]+)$/', $day, $m)) {
                         $occurrence = intval($m[1]);
                         $day = $m[2];
                     }
 
                     if (isset($this->weekday_map[$day])) {
                         // @TODO: libkolabxml does not support BYSETPOS, neither we.
                         // However, we can convert most common cases to BYDAY
                         if (!$occurrence && $freq == 'MONTHLY' && !empty($bysetpos)) {
                             foreach ($bysetpos as $pos) {
                                 $byday->push(new DayPos(intval($pos), $this->weekday_map[$day]));
                             }
                         }
                         else {
                             $byday->push(new DayPos($occurrence, $this->weekday_map[$day]));
                         }
                     }
                 }
                 $rr->setByday($byday);
             }
 
             if ($object['recurrence']['BYMONTHDAY']) {
                 $bymday = new vectori;
                 foreach (explode(',', $object['recurrence']['BYMONTHDAY']) as $day)
                     $bymday->push(intval($day));
                 $rr->setBymonthday($bymday);
             }
 
             if ($object['recurrence']['BYMONTH']) {
                 $bymonth = new vectori;
                 foreach (explode(',', $object['recurrence']['BYMONTH']) as $month)
                     $bymonth->push(intval($month));
                 $rr->setBymonth($bymonth);
             }
 
             if ($object['recurrence']['COUNT'])
                 $rr->setCount(intval($object['recurrence']['COUNT']));
             else if ($object['recurrence']['UNTIL'])
                 $rr->setEnd(self::get_datetime($object['recurrence']['UNTIL'], null, true, $start_tz));
 
             if ($rr->isValid()) {
                 // add exception dates (only if recurrence rule is valid)
                 $exdates = new vectordatetime;
                 foreach ((array)$object['recurrence']['EXDATE'] as $exdate)
                     $exdates->push(self::get_datetime($exdate, null, true, $start_tz));
                 $this->obj->setExceptionDates($exdates);
             }
             else {
                 rcube::raise_error(array(
                     'code' => 600, 'type' => 'php',
                     'file' => __FILE__, 'line' => __LINE__,
                     'message' => "Invalid event recurrence rule: " . json_encode($object['recurrence']),
                 ), true);
             }
         }
 
         $this->obj->setRecurrenceRule($rr);
 
         // save recurrence dates (aka RDATE)
         if (!empty($object['recurrence']['RDATE'])) {
             $rdates = new vectordatetime;
             foreach ((array)$object['recurrence']['RDATE'] as $rdate)
                 $rdates->push(self::get_datetime($rdate, null, true, $start_tz));
             $this->obj->setRecurrenceDates($rdates);
         }
 
         // save alarm(s)
         $valarms = new vectoralarm;
         $valarm_hashes = array();
         if ($object['valarms']) {
             foreach ($object['valarms'] as $valarm) {
                 if (!array_key_exists($valarm['action'], $this->alarm_type_map)) {
                     continue;  // skip unknown alarm types
                 }
 
                 // Get rid of duplicates, some CalDAV clients can set them
                 $hash = serialize($valarm);
                 if (in_array($hash, $valarm_hashes)) {
                     continue;
                 }
                 $valarm_hashes[] = $hash;
 
                 if ($valarm['action'] == 'EMAIL') {
                     $recipients = new vectorcontactref;
                     foreach (($valarm['attendees'] ?: array($object['_owner'])) as $email) {
                         $recipients->push(new ContactReference(ContactReference::EmailReference, $email));
                     }
                     $alarm = new Alarm(
                         strval($valarm['summary'] ?: $object['title']),
                         strval($valarm['description'] ?: $object['description']),
                         $recipients
                     );
                 }
                 else if ($valarm['action'] == 'AUDIO') {
                     $attach = new Attachment;
                     $attach->setUri($valarm['uri'] ?: 'null', 'unknown');
                     $alarm = new Alarm($attach);
                 }
                 else {
                     // action == DISPLAY
                     $alarm = new Alarm(strval($valarm['summary'] ?: $object['title']));
                 }
 
                 if (is_object($valarm['trigger']) && $valarm['trigger'] instanceof DateTime) {
                     $alarm->setStart(self::get_datetime($valarm['trigger'], new DateTimeZone('UTC')));
                 }
                 else if (preg_match('/^@([0-9]+)$/', $valarm['trigger'], $m)) {
                     $alarm->setStart(self::get_datetime($m[1], new DateTimeZone('UTC')));
                 }
                 else {
                     // Support also interval in format without PT, e.g. -10M
                     if (preg_match('/^([-+]*)([0-9]+[DHMS])$/', strtoupper($valarm['trigger']), $m)) {
                         $valarm['trigger'] = $m[1] . ($m[2][strlen($m[2])-1] == 'D' ? 'P' : 'PT') . $m[2];
                     }
 
                     try {
                         $period   = new DateInterval(preg_replace('/[^0-9PTWDHMS]/', '', $valarm['trigger']));
                         $duration = new Duration($period->d, $period->h, $period->i, $period->s, $valarm['trigger'][0] == '-');
                     }
                     catch (Exception $e) {
                         // skip alarm with invalid trigger values
                         rcube::raise_error($e, true);
                         continue;
                     }
 
                     $related = strtoupper($valarm['related']) == 'END' ? kolabformat::End : kolabformat::Start;
                     $alarm->setRelativeStart($duration, $related);
                 }
 
                 if ($valarm['duration']) {
                     try {
                         $d = new DateInterval($valarm['duration']);
                         $duration = new Duration($d->d, $d->h, $d->i, $d->s);
                         $alarm->setDuration($duration, intval($valarm['repeat']));
                     }
                     catch (Exception $e) {
                         // ignore
                     }
                 }
 
                 $valarms->push($alarm);
             }
         }
         // legacy support
         else if ($object['alarms']) {
             list($offset, $type) = explode(":", $object['alarms']);
 
             if ($type == 'EMAIL' && !empty($object['_owner'])) {  // email alarms implicitly go to event owner
                 $recipients = new vectorcontactref;
                 $recipients->push(new ContactReference(ContactReference::EmailReference, $object['_owner']));
                 $alarm = new Alarm($object['title'], strval($object['description']), $recipients);
             }
             else {  // default: display alarm
                 $alarm = new Alarm($object['title']);
             }
 
             if (preg_match('/^@(\d+)/', $offset, $d)) {
                 $alarm->setStart(self::get_datetime($d[1], new DateTimeZone('UTC')));
             }
             else if (preg_match('/^([-+]?)P?T?(\d+)([SMHDW])/', $offset, $d)) {
                 $days = $hours = $minutes = $seconds = 0;
                 switch ($d[3]) {
                     case 'W': $days  = 7*intval($d[2]); break;
                     case 'D': $days    = intval($d[2]); break;
                     case 'H': $hours   = intval($d[2]); break;
                     case 'M': $minutes = intval($d[2]); break;
                     case 'S': $seconds = intval($d[2]); break;
                 }
                 $alarm->setRelativeStart(new Duration($days, $hours, $minutes, $seconds, $d[1] == '-'), $d[1] == '-' ? kolabformat::Start : kolabformat::End);
             }
 
             $valarms->push($alarm);
         }
         $this->obj->setAlarms($valarms);
 
         $this->set_attachments($object);
     }
 
     /**
      * Return the reference date for recurrence and alarms
      *
      * @return mixed DateTime instance of null if no refdate is available
      */
     public function get_reference_date()
     {
         if ($this->data['start'] && $this->data['start'] instanceof DateTime) {
             return $this->data['start'];
         }
 
         return self::php_datetime($this->obj->start());
     }
 
     /**
      * Callback for kolab_storage_cache to get words to index for fulltext search
      *
      * @return array List of words to save in cache
      */
     public function get_words($obj = null)
     {
         $data = '';
         $object = $obj ?: $this->data;
 
         foreach (self::$fulltext_cols as $colname) {
             list($col, $field) = explode(':', $colname);
 
             if ($field) {
                 $a = array();
                 foreach ((array)$object[$col] as $attr)
                     $a[] = $attr[$field];
                 $val = join(' ', $a);
             }
             else {
                 $val = is_array($object[$col]) ? join(' ', $object[$col]) : $object[$col];
             }
 
             if (strlen($val))
                 $data .= $val . ' ';
         }
 
         $words = rcube_utils::normalize_string($data, true);
 
         // collect words from recurrence exceptions
         if (is_array($object['exceptions'])) {
             foreach ($object['exceptions'] as $exception) {
                 $words = array_merge($words, $this->get_words($exception));
             }
         }
 
         return array_unique($words);
     }
 
     /**
      * Callback for kolab_storage_cache to get object specific tags to cache
      *
      * @return array List of tags to save in cache
      */
     public function get_tags($obj = null)
     {
         $tags = array();
         $object = $obj ?: $this->data;
 
         if (!empty($object['valarms'])) {
             $tags[] = 'x-has-alarms';
         }
 
         // create tags reflecting participant status
         if (is_array($object['attendees'])) {
             foreach ($object['attendees'] as $attendee) {
                 if (!empty($attendee['email']) && !empty($attendee['status']))
                     $tags[] = 'x-partstat:' . $attendee['email'] . ':' . strtolower($attendee['status']);
             }
         }
 
         // collect tags from recurrence exceptions
         if (is_array($object['exceptions'])) {
             foreach ($object['exceptions'] as $exception) {
                 $tags = array_merge($tags, $this->get_tags($exception));
             }
         }
 
         if (!empty($object['status'])) {
           $tags[] = 'x-status:' . strtolower($object['status']);
         }
 
         return array_unique($tags);
     }
 
     /**
      * Identify changes considered relevant for scheduling
      * 
      * @param array Hash array with NEW object properties
      * @param array Hash array with OLD object properties
      *
      * @return boolean True if changes affect scheduling, False otherwise
      */
     public function check_rescheduling($object, $old = null)
     {
         $reschedule = false;
 
         if (!is_array($old)) {
             $old = $this->data['uid'] ? $this->data : $this->to_array();
         }
 
         foreach ($this->_scheduling_properties ?: self::$scheduling_properties as $prop) {
             $a = $old[$prop];
             $b = $object[$prop];
             if ($object['allday'] && ($prop == 'start' || $prop == 'end') && $a instanceof DateTime && $b instanceof DateTime) {
                 $a = $a->format('Y-m-d');
                 $b = $b->format('Y-m-d');
             }
             if ($prop == 'recurrence' && is_array($a) && is_array($b)) {
                 unset($a['EXCEPTIONS'], $b['EXCEPTIONS']);
                 $a = array_filter($a);
                 $b = array_filter($b);
 
                 // advanced rrule comparison: no rescheduling if series was shortened
                 if ($a['COUNT'] && $b['COUNT'] && $b['COUNT'] < $a['COUNT']) {
                   unset($a['COUNT'], $b['COUNT']);
                 }
                 else if ($a['UNTIL'] && $b['UNTIL'] && $b['UNTIL'] < $a['UNTIL']) {
                   unset($a['UNTIL'], $b['UNTIL']);
                 }
             }
             if ($a != $b) {
                 $reschedule = true;
                 break;
             }
         }
 
         return $reschedule;
     }
 
     /**
      * Clones into an instance of libcalendaring's extended EventCal class
      *
      * @return mixed EventCal object or false on failure
      */
     public function to_libcal()
     {
         static $error_logged = false;
 
         if (class_exists('kolabcalendaring')) {
             return new EventCal($this->obj);
         }
         else if (!$error_logged) {
             $error_logged = true;
             rcube::raise_error(array(
                 'code'    => 900,
                 'message' => "Required kolabcalendaring module not found"
             ), true);
         }
 
         return false;
     }
 }