plugins/calendar plugins/libkolab

Thomas Brüderli bruederli at kolabsys.com
Tue Jul 3 08:28:46 CEST 2012


 plugins/calendar/drivers/kolab/kolab_calendar.php |    7 
 plugins/calendar/lib/Horde_Date_Recurrence.php    |    3 
 plugins/calendar/lib/Horde_iCalendar.php          |    3 
 plugins/libkolab/bin/get_horde_date.sh            |   38 
 plugins/libkolab/lib/Horde_Date.php               | 1112 +++++++++++++
 plugins/libkolab/lib/Horde_Date_Recurrence.php    | 1768 ++++++++++++++++++++++
 plugins/libkolab/lib/kolab_date_recurrence.php    |  105 +
 7 files changed, 3029 insertions(+), 7 deletions(-)

New commits:
commit 1142a8088600c19f0086eaf68c5fa4a49e56d61d
Author: Thomas Bruederli <thomas at roundcube.net>
Date:   Tue Jul 3 08:25:55 2012 +0200

    Move classes for recurring events/tasks computation to libkolab

diff --git a/plugins/calendar/drivers/kolab/kolab_calendar.php b/plugins/calendar/drivers/kolab/kolab_calendar.php
index 9e9825e..669b28e 100644
--- a/plugins/calendar/drivers/kolab/kolab_calendar.php
+++ b/plugins/calendar/drivers/kolab/kolab_calendar.php
@@ -360,7 +360,7 @@ class kolab_calendar
         raise_error(array(
           'code' => 600, 'type' => 'php',
           'file' => __FILE__, 'line' => __LINE__,
-          'message' => "Error undeleting a contact object $uid from the Kolab server"),
+          'message' => "Error undeleting the event object $uid from the Kolab server"),
         true, false);
     }
 
@@ -373,10 +373,7 @@ class kolab_calendar
    */
   public function _get_recurring_events($event, $start, $end, $event_id = null)
   {
-    // include library class
-    require_once($this->cal->home . '/lib/calendar_recurrence.php');
-    
-    $recurrence = new calendar_recurrence($this->cal, $event);
+    $recurrence = new kolab_date_recurrence($event);
     
     $events = array();
     $duration = $event['end'] - $event['start'];
diff --git a/plugins/calendar/lib/Horde_Date_Recurrence.php b/plugins/calendar/lib/Horde_Date_Recurrence.php
index 379d54a..829a6b8 100644
--- a/plugins/calendar/lib/Horde_Date_Recurrence.php
+++ b/plugins/calendar/lib/Horde_Date_Recurrence.php
@@ -5,7 +5,8 @@
  *   PEAR/Date/Calc.php, Horde/Date/Recurrence.php
  */
 
-require_once(dirname(__FILE__) . '/Horde_Date.php');
+if (!class_exists('Horde_Date'))
+    require_once(dirname(__FILE__) . '/Horde_Date.php');
 
 // {{{ Header
 
diff --git a/plugins/calendar/lib/Horde_iCalendar.php b/plugins/calendar/lib/Horde_iCalendar.php
index f898170..a3ff79d 100644
--- a/plugins/calendar/lib/Horde_iCalendar.php
+++ b/plugins/calendar/lib/Horde_iCalendar.php
@@ -5,7 +5,8 @@
  *   Horde/String.php, Horde/iCalendar.php, Horde/iCalendar/*.php
  */
 
-require_once(dirname(__FILE__) . '/Horde_Date.php');
+if (!class_exists('Horde_Date'))
+    require_once(dirname(__FILE__) . '/Horde_Date.php');
 
 
 $GLOBALS['_HORDE_STRING_CHARSET'] = 'iso-8859-1';
diff --git a/plugins/libkolab/bin/get_horde_date.sh b/plugins/libkolab/bin/get_horde_date.sh
new file mode 100755
index 0000000..c75b7fd
--- /dev/null
+++ b/plugins/libkolab/bin/get_horde_date.sh
@@ -0,0 +1,38 @@
+#!/bin/sh
+
+# Copy Horde_Date_Recurrence classes and dependencies to stdout.
+# This will create a standalone copy of the classes requried for date recurrence computation.
+
+SRCDIR=$1
+
+if [ ! -d "$SRCDIR" ]; then
+  echo "Usage: get_horde_date.sh SRCDIR"
+  echo "Please enter a valid source directory of the Horde libs"
+  exit 1
+fi
+
+echo "<?php
+
+/**
+ * This is a concatenated copy of the following files:
+ *   Horde/Date/Utils.php, Horde/Date/Recurrence.php
+ * Pull the latest version of these files from the PEAR channel of the Horde
+ * project at http://pear.horde.org by installing the Horde_Date package.
+ */
+
+if (!class_exists('Horde_Date'))
+	require_once(dirname(__FILE__) . '/Horde_Date.php');
+
+// minimal required implementation of Horde_Date_Translation to avoid a huge dependency nightmare
+class Horde_Date_Translation
+{
+	function t(\$arg) { return \$arg; }
+	function ngettext(\$sing, \$plur, \$num) { return (\$num > 1 ? \$plur : \$sing); }
+}
+"
+
+sed 's/<?php//; s/?>//' $SRCDIR/Date/Utils.php
+echo "\n"
+sed 's/<?php//; s/?>//' $SRCDIR/Date/Recurrence.php | sed -E "s/Horde_String::/strto/"
+echo "\n"
+
diff --git a/plugins/libkolab/lib/Horde_Date.php b/plugins/libkolab/lib/Horde_Date.php
new file mode 100644
index 0000000..4ddd9d5
--- /dev/null
+++ b/plugins/libkolab/lib/Horde_Date.php
@@ -0,0 +1,1112 @@
+<?php
+/**
+ * Horde Date wrapper/logic class, including some calculation
+ * functions.
+ *
+ * @category Horde
+ * @package  Date
+ *
+ * @TODO in format():
+ *   http://php.net/intldateformatter
+ *
+ * @TODO on timezones:
+ *   http://trac.agavi.org/ticket/1008
+ *   http://trac.agavi.org/changeset/3659
+ *
+ * @TODO on switching to PHP::DateTime:
+ *   The only thing ever stored in the database *IS* Unix timestamps. Doing
+ *   anything other than that is unmanageable, yet some frameworks use 'server
+ *   based' times in their systems, simply because they do not bother with
+ *   daylight saving and only 'serve' one timezone!
+ *
+ *   The second you have to manage 'real' time across timezones then daylight
+ *   saving becomes essential, BUT only on the display side! Since the browser
+ *   only provides a time offset, this is useless and to be honest should simply
+ *   be ignored ( until it is upgraded to provide the correct information ;)
+ *   ). So we need a 'display' function that takes a simple numeric epoch, and a
+ *   separate timezone id into which the epoch is to be 'converted'. My W3C
+ *   mapping works simply because ADOdb then converts that to it's own simple
+ *   offset abbreviation - in my case GMT or BST. As long as DateTime passes the
+ *   full 64 bit number the date range from 100AD is also preserved ( and
+ *   further back if 2 digit years are disabled ). If I want to display the
+ *   'real' timezone with this 'time' then I just add it in place of ADOdb's
+ *   'timezone'. I am tempted to simply adjust the ADOdb class to take a
+ *   timezone in place of the simple GMT switch it currently uses.
+ *
+ *   The return path is just the reverse and simply needs to take the client
+ *   display offset off prior to storage of the UTC epoch. SO we use
+ *   DateTimeZone to get an offset value for the clients timezone and simply add
+ *   or subtract this from a timezone agnostic display on the client end when
+ *   entering new times.
+ *
+ *
+ *   It's not really feasible to store dates in specific timezone, as most
+ *   national/local timezones support DST - and that is a pain to support, as
+ *   eg.  sorting breaks when some timestamps get repeated. That's why it's
+ *   usually better to store datetimes as either UTC datetime or plain unix
+ *   timestamp. I usually go with the former - using database datetime type.
+ */
+
+/**
+ * @category Horde
+ * @package  Date
+ */
+class Horde_Date
+{
+    const DATE_SUNDAY = 0;
+    const DATE_MONDAY = 1;
+    const DATE_TUESDAY = 2;
+    const DATE_WEDNESDAY = 3;
+    const DATE_THURSDAY = 4;
+    const DATE_FRIDAY = 5;
+    const DATE_SATURDAY = 6;
+
+    const MASK_SUNDAY = 1;
+    const MASK_MONDAY = 2;
+    const MASK_TUESDAY = 4;
+    const MASK_WEDNESDAY = 8;
+    const MASK_THURSDAY = 16;
+    const MASK_FRIDAY = 32;
+    const MASK_SATURDAY = 64;
+    const MASK_WEEKDAYS = 62;
+    const MASK_WEEKEND = 65;
+    const MASK_ALLDAYS = 127;
+
+    const MASK_SECOND = 1;
+    const MASK_MINUTE = 2;
+    const MASK_HOUR = 4;
+    const MASK_DAY = 8;
+    const MASK_MONTH = 16;
+    const MASK_YEAR = 32;
+    const MASK_ALLPARTS = 63;
+
+    const DATE_DEFAULT = 'Y-m-d H:i:s';
+    const DATE_JSON = 'Y-m-d\TH:i:s';
+
+    /**
+     * Year
+     *
+     * @var integer
+     */
+    protected $_year;
+
+    /**
+     * Month
+     *
+     * @var integer
+     */
+    protected $_month;
+
+    /**
+     * Day
+     *
+     * @var integer
+     */
+    protected $_mday;
+
+    /**
+     * Hour
+     *
+     * @var integer
+     */
+    protected $_hour = 0;
+
+    /**
+     * Minute
+     *
+     * @var integer
+     */
+    protected $_min = 0;
+
+    /**
+     * Second
+     *
+     * @var integer
+     */
+    protected $_sec = 0;
+
+    /**
+     * String representation of the date's timezone.
+     *
+     * @var string
+     */
+    protected $_timezone;
+
+    /**
+     * Default format for __toString()
+     *
+     * @var string
+     */
+    protected $_defaultFormat = self::DATE_DEFAULT;
+
+    /**
+     * Default specs that are always supported.
+     * @var string
+     */
+    protected static $_defaultSpecs = '%CdDeHImMnRStTyY';
+
+    /**
+     * Internally supported strftime() specifiers.
+     * @var string
+     */
+    protected static $_supportedSpecs = '';
+
+    /**
+     * Map of required correction masks.
+     *
+     * @see __set()
+     *
+     * @var array
+     */
+    protected static $_corrections = array(
+        'year'  => self::MASK_YEAR,
+        'month' => self::MASK_MONTH,
+        'mday'  => self::MASK_DAY,
+        'hour'  => self::MASK_HOUR,
+        'min'   => self::MASK_MINUTE,
+        'sec'   => self::MASK_SECOND,
+    );
+
+    protected $_formatCache = array();
+
+    /**
+     * Builds a new date object. If $date contains date parts, use them to
+     * initialize the object.
+     *
+     * Recognized formats:
+     * - arrays with keys 'year', 'month', 'mday', 'day'
+     *   'hour', 'min', 'minute', 'sec'
+     * - objects with properties 'year', 'month', 'mday', 'hour', 'min', 'sec'
+     * - yyyy-mm-dd hh:mm:ss
+     * - yyyymmddhhmmss
+     * - yyyymmddThhmmssZ
+     * - yyyymmdd (might conflict with unix timestamps between 31 Oct 1966 and
+     *   03 Mar 1973)
+     * - unix timestamps
+     * - anything parsed by strtotime()/DateTime.
+     *
+     * @throws Horde_Date_Exception
+     */
+    public function __construct($date = null, $timezone = null)
+    {
+        if (!self::$_supportedSpecs) {
+            self::$_supportedSpecs = self::$_defaultSpecs;
+            if (function_exists('nl_langinfo')) {
+                self::$_supportedSpecs .= 'bBpxX';
+            }
+        }
+
+        if (func_num_args() > 2) {
+            // Handle args in order: year month day hour min sec tz
+            $this->_initializeFromArgs(func_get_args());
+            return;
+        }
+
+        $this->_initializeTimezone($timezone);
+
+        if (is_null($date)) {
+            return;
+        }
+
+        if (is_string($date)) {
+            $date = trim($date, '"');
+        }
+
+        if (is_object($date)) {
+            $this->_initializeFromObject($date);
+        } elseif (is_array($date)) {
+            $this->_initializeFromArray($date);
+        } elseif (preg_match('/^(\d{4})-?(\d{2})-?(\d{2})T? ?(\d{2}):?(\d{2}):?(\d{2})(?:\.\d+)?(Z?)$/', $date, $parts)) {
+            $this->_year  = (int)$parts[1];
+            $this->_month = (int)$parts[2];
+            $this->_mday  = (int)$parts[3];
+            $this->_hour  = (int)$parts[4];
+            $this->_min   = (int)$parts[5];
+            $this->_sec   = (int)$parts[6];
+            if ($parts[7]) {
+                $this->_initializeTimezone('UTC');
+            }
+        } elseif (preg_match('/^(\d{4})-?(\d{2})-?(\d{2})$/', $date, $parts) &&
+                  $parts[2] > 0 && $parts[2] <= 12 &&
+                  $parts[3] > 0 && $parts[3] <= 31) {
+            $this->_year  = (int)$parts[1];
+            $this->_month = (int)$parts[2];
+            $this->_mday  = (int)$parts[3];
+            $this->_hour = $this->_min = $this->_sec = 0;
+        } elseif ((string)(int)$date == $date) {
+            // Try as a timestamp.
+            $parts = @getdate($date);
+            if ($parts) {
+                $this->_year  = $parts['year'];
+                $this->_month = $parts['mon'];
+                $this->_mday  = $parts['mday'];
+                $this->_hour  = $parts['hours'];
+                $this->_min   = $parts['minutes'];
+                $this->_sec   = $parts['seconds'];
+            }
+        } else {
+            // Use date_create() so we can catch errors with PHP 5.2. Use
+            // "new DateTime() once we require 5.3.
+            $parsed = date_create($date);
+            if (!$parsed) {
+                throw new Horde_Date_Exception(sprintf(Horde_Date_Translation::t("Failed to parse time string (%s)"), $date));
+            }
+            $parsed->setTimezone(new DateTimeZone(date_default_timezone_get()));
+            $this->_year  = (int)$parsed->format('Y');
+            $this->_month = (int)$parsed->format('m');
+            $this->_mday  = (int)$parsed->format('d');
+            $this->_hour  = (int)$parsed->format('H');
+            $this->_min   = (int)$parsed->format('i');
+            $this->_sec   = (int)$parsed->format('s');
+            $this->_initializeTimezone(date_default_timezone_get());
+        }
+    }
+
+    /**
+     * Returns a simple string representation of the date object
+     *
+     * @return string  This object converted to a string.
+     */
+    public function __toString()
+    {
+        try {
+            return $this->format($this->_defaultFormat);
+        } catch (Exception $e) {
+            return '';
+        }
+    }
+
+    /**
+     * Returns a DateTime object representing this object.
+     *
+     * @return DateTime
+     */
+    public function toDateTime()
+    {
+        $date = new DateTime(null, new DateTimeZone($this->_timezone));
+        $date->setDate($this->_year, $this->_month, $this->_mday);
+        $date->setTime($this->_hour, $this->_min, $this->_sec);
+        return $date;
+    }
+
+    /**
+     * Converts a date in the proleptic Gregorian calendar to the no of days
+     * since 24th November, 4714 B.C.
+     *
+     * Returns the no of days since Monday, 24th November, 4714 B.C. in the
+     * proleptic Gregorian calendar (which is 24th November, -4713 using
+     * 'Astronomical' year numbering, and 1st January, 4713 B.C. in the
+     * proleptic Julian calendar).  This is also the first day of the 'Julian
+     * Period' proposed by Joseph Scaliger in 1583, and the number of days
+     * since this date is known as the 'Julian Day'.  (It is not directly
+     * to do with the Julian calendar, although this is where the name
+     * is derived from.)
+     *
+     * The algorithm is valid for all years (positive and negative), and
+     * also for years preceding 4714 B.C.
+     *
+     * Algorithm is from PEAR::Date_Calc
+     *
+     * @author Monte Ohrt <monte at ispi.net>
+     * @author Pierre-Alain Joye <pajoye at php.net>
+     * @author Daniel Convissor <danielc at php.net>
+     * @author C.A. Woodcock <c01234 at netcomuk.co.uk>
+     *
+     * @return integer  The number of days since 24th November, 4714 B.C.
+     */
+    public function toDays()
+    {
+        if (function_exists('GregorianToJD')) {
+            return gregoriantojd($this->_month, $this->_mday, $this->_year);
+        }
+
+        $day = $this->_mday;
+        $month = $this->_month;
+        $year = $this->_year;
+
+        if ($month > 2) {
+            // March = 0, April = 1, ..., December = 9,
+            // January = 10, February = 11
+            $month -= 3;
+        } else {
+            $month += 9;
+            --$year;
+        }
+
+        $hb_negativeyear = $year < 0;
+        $century         = intval($year / 100);
+        $year            = $year % 100;
+
+        if ($hb_negativeyear) {
+            // Subtract 1 because year 0 is a leap year;
+            // And N.B. that we must treat the leap years as occurring
+            // one year earlier than they do, because for the purposes
+            // of calculation, the year starts on 1st March:
+            //
+            return intval((14609700 * $century + ($year == 0 ? 1 : 0)) / 400) +
+                   intval((1461 * $year + 1) / 4) +
+                   intval((153 * $month + 2) / 5) +
+                   $day + 1721118;
+        } else {
+            return intval(146097 * $century / 4) +
+                   intval(1461 * $year / 4) +
+                   intval((153 * $month + 2) / 5) +
+                   $day + 1721119;
+        }
+    }
+
+    /**
+     * Converts number of days since 24th November, 4714 B.C. (in the proleptic
+     * Gregorian calendar, which is year -4713 using 'Astronomical' year
+     * numbering) to Gregorian calendar date.
+     *
+     * Returned date belongs to the proleptic Gregorian calendar, using
+     * 'Astronomical' year numbering.
+     *
+     * The algorithm is valid for all years (positive and negative), and
+     * also for years preceding 4714 B.C. (i.e. for negative 'Julian Days'),
+     * and so the only limitation is platform-dependent (for 32-bit systems
+     * the maximum year would be something like about 1,465,190 A.D.).
+     *
+     * N.B. Monday, 24th November, 4714 B.C. is Julian Day '0'.
+     *
+     * Algorithm is from PEAR::Date_Calc
+     *
+     * @author Monte Ohrt <monte at ispi.net>
+     * @author Pierre-Alain Joye <pajoye at php.net>
+     * @author Daniel Convissor <danielc at php.net>
+     * @author C.A. Woodcock <c01234 at netcomuk.co.uk>
+     *
+     * @param int    $days   the number of days since 24th November, 4714 B.C.
+     * @param string $format the string indicating how to format the output
+     *
+     * @return  Horde_Date  A Horde_Date object representing the date.
+     */
+    public static function fromDays($days)
+    {
+        if (function_exists('JDToGregorian')) {
+            list($month, $day, $year) = explode('/', JDToGregorian($days));
+        } else {
+            $days = intval($days);
+
+            $days   -= 1721119;
+            $century = floor((4 * $days - 1) / 146097);
+            $days    = floor(4 * $days - 1 - 146097 * $century);
+            $day     = floor($days / 4);
+
+            $year = floor((4 * $day +  3) / 1461);
+            $day  = floor(4 * $day +  3 - 1461 * $year);
+            $day  = floor(($day +  4) / 4);
+
+            $month = floor((5 * $day - 3) / 153);
+            $day   = floor(5 * $day - 3 - 153 * $month);
+            $day   = floor(($day +  5) /  5);
+
+            $year = $century * 100 + $year;
+            if ($month < 10) {
+                $month +=3;
+            } else {
+                $month -=9;
+                ++$year;
+            }
+        }
+
+        return new Horde_Date($year, $month, $day);
+    }
+
+    /**
+     * Getter for the date and time properties.
+     *
+     * @param string $name  One of 'year', 'month', 'mday', 'hour', 'min' or
+     *                      'sec'.
+     *
+     * @return integer  The property value, or null if not set.
+     */
+    public function __get($name)
+    {
+        if ($name == 'day') {
+            $name = 'mday';
+        }
+
+        return $this->{'_' . $name};
+    }
+
+    /**
+     * Setter for the date and time properties.
+     *
+     * @param string $name    One of 'year', 'month', 'mday', 'hour', 'min' or
+     *                        'sec'.
+     * @param integer $value  The property value.
+     */
+    public function __set($name, $value)
+    {
+        if ($name == 'timezone') {
+            $this->_initializeTimezone($value);
+            return;
+        }
+        if ($name == 'day') {
+            $name = 'mday';
+        }
+
+        if ($name != 'year' && $name != 'month' && $name != 'mday' &&
+            $name != 'hour' && $name != 'min' && $name != 'sec') {
+            throw new InvalidArgumentException('Undefined property ' . $name);
+        }
+
+        $down = $value < $this->{'_' . $name};
+        $this->{'_' . $name} = $value;
+        $this->_correct(self::$_corrections[$name], $down);
+        $this->_formatCache = array();
+    }
+
+    /**
+     * Returns whether a date or time property exists.
+     *
+     * @param string $name  One of 'year', 'month', 'mday', 'hour', 'min' or
+     *                      'sec'.
+     *
+     * @return boolen  True if the property exists and is set.
+     */
+    public function __isset($name)
+    {
+        if ($name == 'day') {
+            $name = 'mday';
+        }
+        return ($name == 'year' || $name == 'month' || $name == 'mday' ||
+                $name == 'hour' || $name == 'min' || $name == 'sec') &&
+            isset($this->{'_' . $name});
+    }
+
+    /**
+     * Adds a number of seconds or units to this date, returning a new Date
+     * object.
+     */
+    public function add($factor)
+    {
+        $d = clone($this);
+        if (is_array($factor) || is_object($factor)) {
+            foreach ($factor as $property => $value) {
+                $d->$property += $value;
+            }
+        } else {
+            $d->sec += $factor;
+        }
+
+        return $d;
+    }
+
+    /**
+     * Subtracts a number of seconds or units from this date, returning a new
+     * Horde_Date object.
+     */
+    public function sub($factor)
+    {
+        if (is_array($factor)) {
+            foreach ($factor as &$value) {
+                $value *= -1;
+            }
+        } else {
+            $factor *= -1;
+        }
+
+        return $this->add($factor);
+    }
+
+    /**
+     * Converts this object to a different timezone.
+     *
+     * @param string $timezone  The new timezone.
+     *
+     * @return Horde_Date  This object.
+     */
+    public function setTimezone($timezone)
+    {
+        $date = $this->toDateTime();
+        $date->setTimezone(new DateTimeZone($timezone));
+        $this->_timezone = $timezone;
+        $this->_year     = (int)$date->format('Y');
+        $this->_month    = (int)$date->format('m');
+        $this->_mday     = (int)$date->format('d');
+        $this->_hour     = (int)$date->format('H');
+        $this->_min      = (int)$date->format('i');
+        $this->_sec      = (int)$date->format('s');
+        $this->_formatCache = array();
+        return $this;
+    }
+
+    /**
+     * Sets the default date format used in __toString()
+     *
+     * @param string $format
+     */
+    public function setDefaultFormat($format)
+    {
+        $this->_defaultFormat = $format;
+    }
+
+    /**
+     * Returns the day of the week (0 = Sunday, 6 = Saturday) of this date.
+     *
+     * @return integer  The day of the week.
+     */
+    public function dayOfWeek()
+    {
+        if ($this->_month > 2) {
+            $month = $this->_month - 2;
+            $year = $this->_year;
+        } else {
+            $month = $this->_month + 10;
+            $year = $this->_year - 1;
+        }
+
+        $day = (floor((13 * $month - 1) / 5) +
+                $this->_mday + ($year % 100) +
+                floor(($year % 100) / 4) +
+                floor(($year / 100) / 4) - 2 *
+                floor($year / 100) + 77);
+
+        return (int)($day - 7 * floor($day / 7));
+    }
+
+    /**
+     * Returns the day number of the year (1 to 365/366).
+     *
+     * @return integer  The day of the year.
+     */
+    public function dayOfYear()
+    {
+        return $this->format('z') + 1;
+    }
+
+    /**
+     * Returns the week of the month.
+     *
+     * @return integer  The week number.
+     */
+    public function weekOfMonth()
+    {
+        return ceil($this->_mday / 7);
+    }
+
+    /**
+     * Returns the week of the year, first Monday is first day of first week.
+     *
+     * @return integer  The week number.
+     */
+    public function weekOfYear()
+    {
+        return $this->format('W');
+    }
+
+    /**
+     * Returns the number of weeks in the given year (52 or 53).
+     *
+     * @param integer $year  The year to count the number of weeks in.
+     *
+     * @return integer $numWeeks   The number of weeks in $year.
+     */
+    public static function weeksInYear($year)
+    {
+        // Find the last Thursday of the year.
+        $date = new Horde_Date($year . '-12-31');
+        while ($date->dayOfWeek() != self::DATE_THURSDAY) {
+            --$date->mday;
+        }
+        return $date->weekOfYear();
+    }
+
+    /**
+     * Sets the date of this object to the $nth weekday of $weekday.
+     *
+     * @param integer $weekday  The day of the week (0 = Sunday, etc).
+     * @param integer $nth      The $nth $weekday to set to (defaults to 1).
+     */
+    public function setNthWeekday($weekday, $nth = 1)
+    {
+        if ($weekday < self::DATE_SUNDAY || $weekday > self::DATE_SATURDAY) {
+            return;
+        }
+
+        $this->_mday = 1;
+        $first = $this->dayOfWeek();
+        if ($weekday < $first) {
+            $this->_mday = 8 + $weekday - $first;
+        } else {
+            $this->_mday = $weekday - $first + 1;
+        }
+        $diff = 7 * $nth - 7;
+        $this->_mday += $diff;
+        $this->_correct(self::MASK_DAY, $diff < 0);
+    }
+
+    /**
+     * Is the date currently represented by this object a valid date?
+     *
+     * @return boolean  Validity, counting leap years, etc.
+     */
+    public function isValid()
+    {
+        return ($this->_year >= 0 && $this->_year <= 9999);
+    }
+
+    /**
+     * Compares this date to another date object to see which one is
+     * greater (later). Assumes that the dates are in the same
+     * timezone.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return integer  ==  0 if they are on the same date
+     *                  >=  1 if $this is greater (later)
+     *                  <= -1 if $other is greater (later)
+     */
+    public function compareDate($other)
+    {
+        if (!($other instanceof Horde_Date)) {
+            $other = new Horde_Date($other);
+        }
+
+        if ($this->_year != $other->year) {
+            return $this->_year - $other->year;
+        }
+        if ($this->_month != $other->month) {
+            return $this->_month - $other->month;
+        }
+
+        return $this->_mday - $other->mday;
+    }
+
+    /**
+     * Returns whether this date is after the other.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return boolean  True if this date is after the other.
+     */
+    public function after($other)
+    {
+        return $this->compareDate($other) > 0;
+    }
+
+    /**
+     * Returns whether this date is before the other.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return boolean  True if this date is before the other.
+     */
+    public function before($other)
+    {
+        return $this->compareDate($other) < 0;
+    }
+
+    /**
+     * Returns whether this date is the same like the other.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return boolean  True if this date is the same like the other.
+     */
+    public function equals($other)
+    {
+        return $this->compareDate($other) == 0;
+    }
+
+    /**
+     * Compares this to another date object by time, to see which one
+     * is greater (later). Assumes that the dates are in the same
+     * timezone.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return integer  ==  0 if they are at the same time
+     *                  >=  1 if $this is greater (later)
+     *                  <= -1 if $other is greater (later)
+     */
+    public function compareTime($other)
+    {
+        if (!($other instanceof Horde_Date)) {
+            $other = new Horde_Date($other);
+        }
+
+        if ($this->_hour != $other->hour) {
+            return $this->_hour - $other->hour;
+        }
+        if ($this->_min != $other->min) {
+            return $this->_min - $other->min;
+        }
+
+        return $this->_sec - $other->sec;
+    }
+
+    /**
+     * Compares this to another date object, including times, to see
+     * which one is greater (later). Assumes that the dates are in the
+     * same timezone.
+     *
+     * @param mixed $other  The date to compare to.
+     *
+     * @return integer  ==  0 if they are equal
+     *                  >=  1 if $this is greater (later)
+     *                  <= -1 if $other is greater (later)
+     */
+    public function compareDateTime($other)
+    {
+        if (!($other instanceof Horde_Date)) {
+            $other = new Horde_Date($other);
+        }
+
+        if ($diff = $this->compareDate($other)) {
+            return $diff;
+        }
+
+        return $this->compareTime($other);
+    }
+
+    /**
+     * Returns number of days between this date and another.
+     *
+     * @param Horde_Date $other  The other day to diff with.
+     *
+     * @return integer  The absolute number of days between the two dates.
+     */
+    public function diff($other)
+    {
+        return abs($this->toDays() - $other->toDays());
+    }
+
+    /**
+     * Returns the time offset for local time zone.
+     *
+     * @param boolean $colon  Place a colon between hours and minutes?
+     *
+     * @return string  Timezone offset as a string in the format +HH:MM.
+     */
+    public function tzOffset($colon = true)
+    {
+        return $colon ? $this->format('P') : $this->format('O');
+    }
+
+    /**
+     * Returns the unix timestamp representation of this date.
+     *
+     * @return integer  A unix timestamp.
+     */
+    public function timestamp()
+    {
+        if ($this->_year >= 1970 && $this->_year < 2038) {
+            return mktime($this->_hour, $this->_min, $this->_sec,
+                          $this->_month, $this->_mday, $this->_year);
+        }
+        return $this->format('U');
+    }
+
+    /**
+     * Returns the unix timestamp representation of this date, 12:00am.
+     *
+     * @return integer  A unix timestamp.
+     */
+    public function datestamp()
+    {
+        if ($this->_year >= 1970 && $this->_year < 2038) {
+            return mktime(0, 0, 0, $this->_month, $this->_mday, $this->_year);
+        }
+        $date = new DateTime($this->format('Y-m-d'));
+        return $date->format('U');
+    }
+
+    /**
+     * Formats date and time to be passed around as a short url parameter.
+     *
+     * @return string  Date and time.
+     */
+    public function dateString()
+    {
+        return sprintf('%04d%02d%02d', $this->_year, $this->_month, $this->_mday);
+    }
+
+    /**
+     * Formats date and time to the ISO format used by JSON.
+     *
+     * @return string  Date and time.
+     */
+    public function toJson()
+    {
+        return $this->format(self::DATE_JSON);
+    }
+
+    /**
+     * Formats date and time to the RFC 2445 iCalendar DATE-TIME format.
+     *
+     * @param boolean $floating  Whether to return a floating date-time
+     *                           (without time zone information).
+     *
+     * @return string  Date and time.
+     */
+    public function toiCalendar($floating = false)
+    {
+        if ($floating) {
+            return $this->format('Ymd\THis');
+        }
+        $dateTime = $this->toDateTime();
+        $dateTime->setTimezone(new DateTimeZone('UTC'));
+        return $dateTime->format('Ymd\THis\Z');
+    }
+
+    /**
+     * Formats time using the specifiers available in date() or in the DateTime
+     * class' format() method.
+     *
+     * To format in languages other than English, use strftime() instead.
+     *
+     * @param string $format
+     *
+     * @return string  Formatted time.
+     */
+    public function format($format)
+    {
+        if (!isset($this->_formatCache[$format])) {
+            $this->_formatCache[$format] = $this->toDateTime()->format($format);
+        }
+        return $this->_formatCache[$format];
+    }
+
+    /**
+     * Formats date and time using strftime() format.
+     *
+     * @return string  strftime() formatted date and time.
+     */
+    public function strftime($format)
+    {
+        if (preg_match('/%[^' . self::$_supportedSpecs . ']/', $format)) {
+            return strftime($format, $this->timestamp());
+        } else {
+            return $this->_strftime($format);
+        }
+    }
+
+    /**
+     * Formats date and time using a limited set of the strftime() format.
+     *
+     * @return string  strftime() formatted date and time.
+     */
+    protected function _strftime($format)
+    {
+        return preg_replace(
+            array('/%b/e',
+                  '/%B/e',
+                  '/%C/e',
+                  '/%d/e',
+                  '/%D/e',
+                  '/%e/e',
+                  '/%H/e',
+                  '/%I/e',
+                  '/%m/e',
+                  '/%M/e',
+                  '/%n/',
+                  '/%p/e',
+                  '/%R/e',
+                  '/%S/e',
+                  '/%t/',
+                  '/%T/e',
+                  '/%x/e',
+                  '/%X/e',
+                  '/%y/e',
+                  '/%Y/',
+                  '/%%/'),
+            array('$this->_strftime(Horde_Nls::getLangInfo(constant(\'ABMON_\' . (int)$this->_month)))',
+                  '$this->_strftime(Horde_Nls::getLangInfo(constant(\'MON_\' . (int)$this->_month)))',
+                  '(int)($this->_year / 100)',
+                  'sprintf(\'%02d\', $this->_mday)',
+                  '$this->_strftime(\'%m/%d/%y\')',
+                  'sprintf(\'%2d\', $this->_mday)',
+                  'sprintf(\'%02d\', $this->_hour)',
+                  'sprintf(\'%02d\', $this->_hour == 0 ? 12 : ($this->_hour > 12 ? $this->_hour - 12 : $this->_hour))',
+                  'sprintf(\'%02d\', $this->_month)',
+                  'sprintf(\'%02d\', $this->_min)',
+                  "\n",
+                  '$this->_strftime(Horde_Nls::getLangInfo($this->_hour < 12 ? AM_STR : PM_STR))',
+                  '$this->_strftime(\'%H:%M\')',
+                  'sprintf(\'%02d\', $this->_sec)',
+                  "\t",
+                  '$this->_strftime(\'%H:%M:%S\')',
+                  '$this->_strftime(Horde_Nls::getLangInfo(D_FMT))',
+                  '$this->_strftime(Horde_Nls::getLangInfo(T_FMT))',
+                  'substr(sprintf(\'%04d\', $this->_year), -2)',
+                  (int)$this->_year,
+                  '%'),
+            $format);
+    }
+
+    /**
+     * Corrects any over- or underflows in any of the date's members.
+     *
+     * @param integer $mask  We may not want to correct some overflows.
+     * @param integer $down  Whether to correct the date up or down.
+     */
+    protected function _correct($mask = self::MASK_ALLPARTS, $down = false)
+    {
+        if ($mask & self::MASK_SECOND) {
+            if ($this->_sec < 0 || $this->_sec > 59) {
+                $mask |= self::MASK_MINUTE;
+
+                $this->_min += (int)($this->_sec / 60);
+                $this->_sec %= 60;
+                if ($this->_sec < 0) {
+                    $this->_min--;
+                    $this->_sec += 60;
+                }
+            }
+        }
+
+        if ($mask & self::MASK_MINUTE) {
+            if ($this->_min < 0 || $this->_min > 59) {
+                $mask |= self::MASK_HOUR;
+
+                $this->_hour += (int)($this->_min / 60);
+                $this->_min %= 60;
+                if ($this->_min < 0) {
+                    $this->_hour--;
+                    $this->_min += 60;
+                }
+            }
+        }
+
+        if ($mask & self::MASK_HOUR) {
+            if ($this->_hour < 0 || $this->_hour > 23) {
+                $mask |= self::MASK_DAY;
+
+                $this->_mday += (int)($this->_hour / 24);
+                $this->_hour %= 24;
+                if ($this->_hour < 0) {
+                    $this->_mday--;
+                    $this->_hour += 24;
+                }
+            }
+        }
+
+        if ($mask & self::MASK_MONTH) {
+            $this->_correctMonth($down);
+            /* When correcting the month, always correct the day too. Months
+             * have different numbers of days. */
+            $mask |= self::MASK_DAY;
+        }
+
+        if ($mask & self::MASK_DAY) {
+            while ($this->_mday > 28 &&
+                   $this->_mday > Horde_Date_Utils::daysInMonth($this->_month, $this->_year)) {
+                if ($down) {
+                    $this->_mday -= Horde_Date_Utils::daysInMonth($this->_month + 1, $this->_year) - Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
+                } else {
+                    $this->_mday -= Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
+                    $this->_month++;
+                }
+                $this->_correctMonth($down);
+            }
+            while ($this->_mday < 1) {
+                --$this->_month;
+                $this->_correctMonth($down);
+                $this->_mday += Horde_Date_Utils::daysInMonth($this->_month, $this->_year);
+            }
+        }
+    }
+
+    /**
+     * Corrects the current month.
+     *
+     * This cannot be done in _correct() because that would also trigger a
+     * correction of the day, which would result in an infinite loop.
+     *
+     * @param integer $down  Whether to correct the date up or down.
+     */
+    protected function _correctMonth($down = false)
+    {
+        $this->_year += (int)($this->_month / 12);
+        $this->_month %= 12;
+        if ($this->_month < 1) {
+            $this->_year--;
+            $this->_month += 12;
+        }
+    }
+
+    /**
+     * Handles args in order: year month day hour min sec tz
+     */
+    protected function _initializeFromArgs($args)
+    {
+        $tz = (isset($args[6])) ? array_pop($args) : null;
+        $this->_initializeTimezone($tz);
+
+        $args = array_slice($args, 0, 6);
+        $keys = array('year' => 1, 'month' => 1, 'mday' => 1, 'hour' => 0, 'min' => 0, 'sec' => 0);
+        $date = array_combine(array_slice(array_keys($keys), 0, count($args)), $args);
+        $date = array_merge($keys, $date);
+
+        $this->_initializeFromArray($date);
+    }
+
+    protected function _initializeFromArray($date)
+    {
+        if (isset($date['year']) && is_string($date['year']) && strlen($date['year']) == 2) {
+            if ($date['year'] > 70) {
+                $date['year'] += 1900;
+            } else {
+                $date['year'] += 2000;
+            }
+        }
+
+        foreach ($date as $key => $val) {
+            if (in_array($key, array('year', 'month', 'mday', 'hour', 'min', 'sec'))) {
+                $this->{'_'. $key} = (int)$val;
+            }
+        }
+
+        // If $date['day'] is present and numeric we may have been passed
+        // a Horde_Form_datetime array.
+        if (isset($date['day']) &&
+            (string)(int)$date['day'] == $date['day']) {
+            $this->_mday = (int)$date['day'];
+        }
+        // 'minute' key also from Horde_Form_datetime
+        if (isset($date['minute']) &&
+            (string)(int)$date['minute'] == $date['minute']) {
+            $this->_min = (int)$date['minute'];
+        }
+
+        $this->_correct();
+    }
+
+    protected function _initializeFromObject($date)
+    {
+        if ($date instanceof DateTime) {
+            $this->_year  = (int)$date->format('Y');
+            $this->_month = (int)$date->format('m');
+            $this->_mday  = (int)$date->format('d');
+            $this->_hour  = (int)$date->format('H');
+            $this->_min   = (int)$date->format('i');
+            $this->_sec   = (int)$date->format('s');
+            $this->_initializeTimezone($date->getTimezone()->getName());
+        } else {
+            $is_horde_date = $date instanceof Horde_Date;
+            foreach (array('year', 'month', 'mday', 'hour', 'min', 'sec') as $key) {
+                if ($is_horde_date || isset($date->$key)) {
+                    $this->{'_' . $key} = (int)$date->$key;
+                }
+            }
+            if (!$is_horde_date) {
+                $this->_correct();
+            } else {
+                $this->_initializeTimezone($date->timezone);
+            }
+        }
+    }
+
+    protected function _initializeTimezone($timezone)
+    {
+        if (empty($timezone)) {
+            $timezone = date_default_timezone_get();
+        }
+        $this->_timezone = $timezone;
+    }
+
+}
diff --git a/plugins/libkolab/lib/Horde_Date_Recurrence.php b/plugins/libkolab/lib/Horde_Date_Recurrence.php
new file mode 100644
index 0000000..2171a47
--- /dev/null
+++ b/plugins/libkolab/lib/Horde_Date_Recurrence.php
@@ -0,0 +1,1768 @@
+<?php
+
+/**
+ * This is a concatenated copy of the following files:
+ *   Horde/Date.php, Horde/Date/Utils.php, Horde/Date/Recurrence.php
+ * Pull the latest version of these files from the PEAR channel of the Horde
+ * project at http://pear.horde.org by installing the Horde_Date package.
+ */
+
+if (!class_exists('Horde_Date'))
+	require_once(dirname(__FILE__) . '/Horde_Date.php');
+
+// minimal required implementation of Horde_Date_Translation to avoid a huge dependency nightmare
+class Horde_Date_Translation
+{
+	function t($arg) { return $arg; }
+	function ngettext($sing, $plur, $num) { return ($num > 1 ? $plur : $sing); }
+}
+
+
+/**
+ * @category Horde
+ * @package  Date
+ */
+
+/**
+ * Horde Date wrapper/logic class, including some calculation
+ * functions.
+ *
+ * @category Horde
+ * @package  Date
+ */
+class Horde_Date_Utils
+{
+    /**
+     * Returns whether a year is a leap year.
+     *
+     * @param integer $year  The year.
+     *
+     * @return boolean  True if the year is a leap year.
+     */
+    public static function isLeapYear($year)
+    {
+        if (strlen($year) != 4 || preg_match('/\D/', $year)) {
+            return false;
+        }
+
+        return (($year % 4 == 0 && $year % 100 != 0) || $year % 400 == 0);
+    }
+
+    /**
+     * Returns the date of the year that corresponds to the first day of the
+     * given week.
+     *
+     * @param integer $week  The week of the year to find the first day of.
+     * @param integer $year  The year to calculate for.
+     *
+     * @return Horde_Date  The date of the first day of the given week.
+     */
+    public static function firstDayOfWeek($week, $year)
+    {
+        return new Horde_Date(sprintf('%04dW%02d', $year, $week));
+    }
+
+    /**
+     * Returns the number of days in the specified month.
+     *
+     * @param integer $month  The month
+     * @param integer $year   The year.
+     *
+     * @return integer  The number of days in the month.
+     */
+    public static function daysInMonth($month, $year)
+    {
+        static $cache = array();
+        if (!isset($cache[$year][$month])) {
+            $date = new DateTime(sprintf('%04d-%02d-01', $year, $month));
+            $cache[$year][$month] = $date->format('t');
+        }
+        return $cache[$year][$month];
+    }
+
+    /**
+     * Returns a relative, natural language representation of a timestamp
+     *
+     * @todo Wider range of values ... maybe future time as well?
+     * @todo Support minimum resolution parameter.
+     *
+     * @param mixed $time          The time. Any format accepted by Horde_Date.
+     * @param string $date_format  Format to display date if timestamp is
+     *                             more then 1 day old.
+     * @param string $time_format  Format to display time if timestamp is 1
+     *                             day old.
+     *
+     * @return string  The relative time (i.e. 2 minutes ago)
+     */
+    public static function relativeDateTime($time, $date_format = '%x',
+                                            $time_format = '%X')
+    {
+        $date = new Horde_Date($time);
+
+        $delta = time() - $date->timestamp();
+        if ($delta < 60) {
+            return sprintf(Horde_Date_Translation::ngettext("%d second ago", "%d seconds ago", $delta), $delta);
+        }
+
+        $delta = round($delta / 60);
+        if ($delta < 60) {
+            return sprintf(Horde_Date_Translation::ngettext("%d minute ago", "%d minutes ago", $delta), $delta);
+        }
+
+        $delta = round($delta / 60);
+        if ($delta < 24) {
+            return sprintf(Horde_Date_Translation::ngettext("%d hour ago", "%d hours ago", $delta), $delta);
+        }
+
+        if ($delta > 24 && $delta < 48) {
+            $date = new Horde_Date($time);
+            return sprintf(Horde_Date_Translation::t("yesterday at %s"), $date->strftime($time_format));
+        }
+
+        $delta = round($delta / 24);
+        if ($delta < 7) {
+            return sprintf(Horde_Date_Translation::t("%d days ago"), $delta);
+        }
+
+        if (round($delta / 7) < 5) {
+            $delta = round($delta / 7);
+            return sprintf(Horde_Date_Translation::ngettext("%d week ago", "%d weeks ago", $delta), $delta);
+        }
+
+        // Default to the user specified date format.
+        return $date->strftime($date_format);
+    }
+
+    /**
+     * Tries to convert strftime() formatters to date() formatters.
+     *
+     * Unsupported formatters will be removed.
+     *
+     * @param string $format  A strftime() formatting string.
+     *
+     * @return string  A date() formatting string.
+     */
+    public static function strftime2date($format)
+    {
+        $replace = array(
+            '/%a/'  => 'D',
+            '/%A/'  => 'l',
+            '/%d/'  => 'd',
+            '/%e/'  => 'j',
+            '/%j/'  => 'z',
+            '/%u/'  => 'N',
+            '/%w/'  => 'w',
+            '/%U/'  => '',
+            '/%V/'  => 'W',
+            '/%W/'  => '',
+            '/%b/'  => 'M',
+            '/%B/'  => 'F',
+            '/%h/'  => 'M',
+            '/%m/'  => 'm',
+            '/%C/'  => '',
+            '/%g/'  => '',
+            '/%G/'  => 'o',
+            '/%y/'  => 'y',
+            '/%Y/'  => 'Y',
+            '/%H/'  => 'H',
+            '/%I/'  => 'h',
+            '/%i/'  => 'g',
+            '/%M/'  => 'i',
+            '/%p/'  => 'A',
+            '/%P/'  => 'a',
+            '/%r/'  => 'h:i:s A',
+            '/%R/'  => 'H:i',
+            '/%S/'  => 's',
+            '/%T/'  => 'H:i:s',
+            '/%X/e' => 'Horde_Date_Utils::strftime2date(Horde_Nls::getLangInfo(T_FMT))',
+            '/%z/'  => 'O',
+            '/%Z/'  => '',
+            '/%c/'  => '',
+            '/%D/'  => 'm/d/y',
+            '/%F/'  => 'Y-m-d',
+            '/%s/'  => 'U',
+            '/%x/e' => 'Horde_Date_Utils::strftime2date(Horde_Nls::getLangInfo(D_FMT))',
+            '/%n/'  => "\n",
+            '/%t/'  => "\t",
+            '/%%/'  => '%'
+        );
+
+        return preg_replace(array_keys($replace), array_values($replace), $format);
+    }
+
+}
+
+
+
+/**
+ * This file contains the Horde_Date_Recurrence class and according constants.
+ *
+ * Copyright 2007-2012 Horde LLC (http://www.horde.org/)
+ *
+ * See the enclosed file COPYING for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  Date
+ */
+
+/**
+ * The Horde_Date_Recurrence class implements algorithms for calculating
+ * recurrences of events, including several recurrence types, intervals,
+ * exceptions, and conversion from and to vCalendar and iCalendar recurrence
+ * rules.
+ *
+ * All methods expecting dates as parameters accept all values that the
+ * Horde_Date constructor accepts, i.e. a timestamp, another Horde_Date
+ * object, an ISO time string or a hash.
+ *
+ * @author   Jan Schneider <jan at horde.org>
+ * @category Horde
+ * @package  Date
+ */
+class Horde_Date_Recurrence
+{
+    /** No Recurrence **/
+    const RECUR_NONE = 0;
+
+    /** Recurs daily. */
+    const RECUR_DAILY = 1;
+
+    /** Recurs weekly. */
+    const RECUR_WEEKLY = 2;
+
+    /** Recurs monthly on the same date. */
+    const RECUR_MONTHLY_DATE = 3;
+
+    /** Recurs monthly on the same week day. */
+    const RECUR_MONTHLY_WEEKDAY = 4;
+
+    /** Recurs yearly on the same date. */
+    const RECUR_YEARLY_DATE = 5;
+
+    /** Recurs yearly on the same day of the year. */
+    const RECUR_YEARLY_DAY = 6;
+
+    /** Recurs yearly on the same week day. */
+    const RECUR_YEARLY_WEEKDAY = 7;
+
+    /**
+     * The start time of the event.
+     *
+     * @var Horde_Date
+     */
+    public $start;
+
+    /**
+     * The end date of the recurrence interval.
+     *
+     * @var Horde_Date
+     */
+    public $recurEnd = null;
+
+    /**
+     * The number of recurrences.
+     *
+     * @var integer
+     */
+    public $recurCount = null;
+
+    /**
+     * The type of recurrence this event follows. RECUR_* constant.
+     *
+     * @var integer
+     */
+    public $recurType = self::RECUR_NONE;
+
+    /**
+     * The length of time between recurrences. The time unit depends on the
+     * recurrence type.
+     *
+     * @var integer
+     */
+    public $recurInterval = 1;
+
+    /**
+     * Any additional recurrence data.
+     *
+     * @var integer
+     */
+    public $recurData = null;
+
+    /**
+     * All the exceptions from recurrence for this event.
+     *
+     * @var array
+     */
+    public $exceptions = array();
+
+    /**
+     * All the dates this recurrence has been marked as completed.
+     *
+     * @var array
+     */
+    public $completions = array();
+
+    /**
+     * Constructor.
+     *
+     * @param Horde_Date $start  Start of the recurring event.
+     */
+    public function __construct($start)
+    {
+        $this->start = new Horde_Date($start);
+    }
+
+    /**
+     * Resets the class properties.
+     */
+    public function reset()
+    {
+        $this->recurEnd = null;
+        $this->recurCount = null;
+        $this->recurType = self::RECUR_NONE;
+        $this->recurInterval = 1;
+        $this->recurData = null;
+        $this->exceptions = array();
+        $this->completions = array();
+    }
+
+    /**
+     * Checks if this event recurs on a given day of the week.
+     *
+     * @param integer $dayMask  A mask consisting of Horde_Date::MASK_*
+     *                          constants specifying the day(s) to check.
+     *
+     * @return boolean  True if this event recurs on the given day(s).
+     */
+    public function recurOnDay($dayMask)
+    {
+        return ($this->recurData & $dayMask);
+    }
+
+    /**
+     * Specifies the days this event recurs on.
+     *
+     * @param integer $dayMask  A mask consisting of Horde_Date::MASK_*
+     *                          constants specifying the day(s) to recur on.
+     */
+    public function setRecurOnDay($dayMask)
+    {
+        $this->recurData = $dayMask;
+    }
+
+    /**
+     * Returns the days this event recurs on.
+     *
+     * @return integer  A mask consisting of Horde_Date::MASK_* constants
+     *                  specifying the day(s) this event recurs on.
+     */
+    public function getRecurOnDays()
+    {
+        return $this->recurData;
+    }
+
+    /**
+     * Returns whether this event has a specific recurrence type.
+     *
+     * @param integer $recurrence  RECUR_* constant of the
+     *                             recurrence type to check for.
+     *
+     * @return boolean  True if the event has the specified recurrence type.
+     */
+    public function hasRecurType($recurrence)
+    {
+        return ($recurrence == $this->recurType);
+    }
+
+    /**
+     * Sets a recurrence type for this event.
+     *
+     * @param integer $recurrence  A RECUR_* constant.
+     */
+    public function setRecurType($recurrence)
+    {
+        $this->recurType = $recurrence;
+    }
+
+    /**
+     * Returns recurrence type of this event.
+     *
+     * @return integer  A RECUR_* constant.
+     */
+    public function getRecurType()
+    {
+        return $this->recurType;
+    }
+
+    /**
+     * Returns a description of this event's recurring type.
+     *
+     * @return string  Human readable recurring type.
+     */
+    public function getRecurName()
+    {
+        switch ($this->getRecurType()) {
+        case self::RECUR_NONE: return Horde_Date_Translation::t("No recurrence");
+        case self::RECUR_DAILY: return Horde_Date_Translation::t("Daily");
+        case self::RECUR_WEEKLY: return Horde_Date_Translation::t("Weekly");
+        case self::RECUR_MONTHLY_DATE:
+        case self::RECUR_MONTHLY_WEEKDAY: return Horde_Date_Translation::t("Monthly");
+        case self::RECUR_YEARLY_DATE:
+        case self::RECUR_YEARLY_DAY:
+        case self::RECUR_YEARLY_WEEKDAY: return Horde_Date_Translation::t("Yearly");
+        }
+    }
+
+    /**
+     * Sets the length of time between recurrences of this event.
+     *
+     * @param integer $interval  The time between recurrences.
+     */
+    public function setRecurInterval($interval)
+    {
+        if ($interval > 0) {
+            $this->recurInterval = $interval;
+        }
+    }
+
+    /**
+     * Retrieves the length of time between recurrences of this event.
+     *
+     * @return integer  The number of seconds between recurrences.
+     */
+    public function getRecurInterval()
+    {
+        return $this->recurInterval;
+    }
+
+    /**
+     * Sets the number of recurrences of this event.
+     *
+     * @param integer $count  The number of recurrences.
+     */
+    public function setRecurCount($count)
+    {
+        if ($count > 0) {
+            $this->recurCount = (int)$count;
+            // Recurrence counts and end dates are mutually exclusive.
+            $this->recurEnd = null;
+        } else {
+            $this->recurCount = null;
+        }
+    }
+
+    /**
+     * Retrieves the number of recurrences of this event.
+     *
+     * @return integer  The number recurrences.
+     */
+    public function getRecurCount()
+    {
+        return $this->recurCount;
+    }
+
+    /**
+     * Returns whether this event has a recurrence with a fixed count.
+     *
+     * @return boolean  True if this recurrence has a fixed count.
+     */
+    public function hasRecurCount()
+    {
+        return isset($this->recurCount);
+    }
+
+    /**
+     * Sets the start date of the recurrence interval.
+     *
+     * @param Horde_Date $start  The recurrence start.
+     */
+    public function setRecurStart($start)
+    {
+        $this->start = clone $start;
+    }
+
+    /**
+     * Retrieves the start date of the recurrence interval.
+     *
+     * @return Horde_Date  The recurrence start.
+     */
+    public function getRecurStart()
+    {
+        return $this->start;
+    }
+
+    /**
+     * Sets the end date of the recurrence interval.
+     *
+     * @param Horde_Date $end  The recurrence end.
+     */
+    public function setRecurEnd($end)
+    {
+        if (!empty($end)) {
+            // Recurrence counts and end dates are mutually exclusive.
+            $this->recurCount = null;
+            $this->recurEnd = clone $end;
+        } else {
+            $this->recurEnd = $end;
+        }
+    }
+
+    /**
+     * Retrieves the end date of the recurrence interval.
+     *
+     * @return Horde_Date  The recurrence end.
+     */
+    public function getRecurEnd()
+    {
+        return $this->recurEnd;
+    }
+
+    /**
+     * Returns whether this event has a recurrence end.
+     *
+     * @return boolean  True if this recurrence ends.
+     */
+    public function hasRecurEnd()
+    {
+        return isset($this->recurEnd) && isset($this->recurEnd->year) &&
+            $this->recurEnd->year != 9999;
+    }
+
+    /**
+     * Finds the next recurrence of this event that's after $afterDate.
+     *
+     * @param Horde_Date|string $after  Return events after this date.
+     *
+     * @return Horde_Date|boolean  The date of the next recurrence or false
+     *                             if the event does not recur after
+     *                             $afterDate.
+     */
+    public function nextRecurrence($after)
+    {
+        if (!($after instanceof Horde_Date)) {
+            $after = new Horde_Date($after);
+        } else {
+            $after = clone($after);
+        }
+
+        // Make sure $after and $this->start are in the same TZ
+        $after->setTimezone($this->start->timezone);
+        if ($this->start->compareDateTime($after) >= 0) {
+            return clone $this->start;
+        }
+
+        if ($this->recurInterval == 0) {
+            return false;
+        }
+
+        switch ($this->getRecurType()) {
+        case self::RECUR_DAILY:
+            $diff = $this->start->diff($after);
+            $recur = ceil($diff / $this->recurInterval);
+            if ($this->recurCount && $recur >= $this->recurCount) {
+                return false;
+            }
+
+            $recur *= $this->recurInterval;
+            $next = $this->start->add(array('day' => $recur));
+            if ((!$this->hasRecurEnd() ||
+                 $next->compareDateTime($this->recurEnd) <= 0) &&
+                $next->compareDateTime($after) >= 0) {
+                return $next;
+            }
+            break;
+
+        case self::RECUR_WEEKLY:
+            if (empty($this->recurData)) {
+                return false;
+            }
+
+            $start_week = Horde_Date_Utils::firstDayOfWeek($this->start->format('W'),
+                                                           $this->start->year);
+            $start_week->timezone = $this->start->timezone;
+            $start_week->hour = $this->start->hour;
+            $start_week->min  = $this->start->min;
+            $start_week->sec  = $this->start->sec;
+
+            // Make sure we are not at the ISO-8601 first week of year while
+            // still in month 12...OR in the ISO-8601 last week of year while
+            // in month 1 and adjust the year accordingly.
+            $week = $after->format('W');
+            if ($week == 1 && $after->month == 12) {
+                $theYear = $after->year + 1;
+            } elseif ($week >= 52 && $after->month == 1) {
+                $theYear = $after->year - 1;
+            } else {
+                $theYear = $after->year;
+            }
+
+            $after_week = Horde_Date_Utils::firstDayOfWeek($week, $theYear);
+            $after_week->timezone = $this->start->timezone;
+            $after_week_end = clone $after_week;
+            $after_week_end->mday += 7;
+
+            $diff = $start_week->diff($after_week);
+            $interval = $this->recurInterval * 7;
+            $repeats = floor($diff / $interval);
+            if ($diff % $interval < 7) {
+                $recur = $diff;
+            } else {
+                /**
+                 * If the after_week is not in the first week interval the
+                 * search needs to skip ahead a complete interval. The way it is
+                 * calculated here means that an event that occurs every second
+                 * week on Monday and Wednesday with the event actually starting
+                 * on Tuesday or Wednesday will only have one incidence in the
+                 * first week.
+                 */
+                $recur = $interval * ($repeats + 1);
+            }
+
+            if ($this->hasRecurCount()) {
+                $recurrences = 0;
+                /**
+                 * Correct the number of recurrences by the number of events
+                 * that lay between the start of the start week and the
+                 * recurrence start.
+                 */
+                $next = clone $start_week;
+                while ($next->compareDateTime($this->start) < 0) {
+                    if ($this->recurOnDay((int)pow(2, $next->dayOfWeek()))) {
+                        $recurrences--;
+                    }
+                    ++$next->mday;
+                }
+                if ($repeats > 0) {
+                    $weekdays = $this->recurData;
+                    $total_recurrences_per_week = 0;
+                    while ($weekdays > 0) {
+                        if ($weekdays % 2) {
+                            $total_recurrences_per_week++;
+                        }
+                        $weekdays = ($weekdays - ($weekdays % 2)) / 2;
+                    }
+                    $recurrences += $total_recurrences_per_week * $repeats;
+                }
+            }
+
+            $next = clone $start_week;
+            $next->mday += $recur;
+            while ($next->compareDateTime($after) < 0 &&
+                   $next->compareDateTime($after_week_end) < 0) {
+                if ($this->hasRecurCount()
+                    && $next->compareDateTime($after) < 0
+                    && $this->recurOnDay((int)pow(2, $next->dayOfWeek()))) {
+                    $recurrences++;
+                }
+                ++$next->mday;
+            }
+            if ($this->hasRecurCount() &&
+                $recurrences >= $this->recurCount) {
+                return false;
+            }
+            if (!$this->hasRecurEnd() ||
+                $next->compareDateTime($this->recurEnd) <= 0) {
+                if ($next->compareDateTime($after_week_end) >= 0) {
+                    return $this->nextRecurrence($after_week_end);
+                }
+                while (!$this->recurOnDay((int)pow(2, $next->dayOfWeek())) &&
+                       $next->compareDateTime($after_week_end) < 0) {
+                    ++$next->mday;
+                }
+                if (!$this->hasRecurEnd() ||
+                    $next->compareDateTime($this->recurEnd) <= 0) {
+                    if ($next->compareDateTime($after_week_end) >= 0) {
+                        return $this->nextRecurrence($after_week_end);
+                    } else {
+                        return $next;
+                    }
+                }
+            }
+            break;
+
+        case self::RECUR_MONTHLY_DATE:
+            $start = clone $this->start;
+            if ($after->compareDateTime($start) < 0) {
+                $after = clone $start;
+            } else {
+                $after = clone $after;
+            }
+
+            // If we're starting past this month's recurrence of the event,
+            // look in the next month on the day the event recurs.
+            if ($after->mday > $start->mday) {
+                ++$after->month;
+                $after->mday = $start->mday;
+            }
+
+            // Adjust $start to be the first match.
+            $offset = ($after->month - $start->month) + ($after->year - $start->year) * 12;
+            $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
+
+            if ($this->recurCount &&
+                ($offset / $this->recurInterval) >= $this->recurCount) {
+                return false;
+            }
+            $start->month += $offset;
+            $count = $offset / $this->recurInterval;
+
+            do {
+                if ($this->recurCount &&
+                    $count++ >= $this->recurCount) {
+                    return false;
+                }
+
+                // Bail if we've gone past the end of recurrence.
+                if ($this->hasRecurEnd() &&
+                    $this->recurEnd->compareDateTime($start) < 0) {
+                    return false;
+                }
+                if ($start->isValid()) {
+                    return $start;
+                }
+
+                // If the interval is 12, and the date isn't valid, then we
+                // need to see if February 29th is an option. If not, then the
+                // event will _never_ recur, and we need to stop checking to
+                // avoid an infinite loop.
+                if ($this->recurInterval == 12 && ($start->month != 2 || $start->mday > 29)) {
+                    return false;
+                }
+
+                // Add the recurrence interval.
+                $start->month += $this->recurInterval;
+            } while (true);
+
+            break;
+
+        case self::RECUR_MONTHLY_WEEKDAY:
+            // Start with the start date of the event.
+            $estart = clone $this->start;
+
+            // What day of the week, and week of the month, do we recur on?
+            $nth = ceil($this->start->mday / 7);
+            $weekday = $estart->dayOfWeek();
+
+            // Adjust $estart to be the first candidate.
+            $offset = ($after->month - $estart->month) + ($after->year - $estart->year) * 12;
+            $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
+
+            // Adjust our working date until it's after $after.
+            $estart->month += $offset - $this->recurInterval;
+
+            $count = $offset / $this->recurInterval;
+            do {
+                if ($this->recurCount &&
+                    $count++ >= $this->recurCount) {
+                    return false;
+                }
+
+                $estart->month += $this->recurInterval;
+
+                $next = clone $estart;
+                $next->setNthWeekday($weekday, $nth);
+
+                if ($next->compareDateTime($after) < 0) {
+                    // We haven't made it past $after yet, try again.
+                    continue;
+                }
+                if ($this->hasRecurEnd() &&
+                    $next->compareDateTime($this->recurEnd) > 0) {
+                    // We've gone past the end of recurrence; we can give up
+                    // now.
+                    return false;
+                }
+
+                // We have a candidate to return.
+                break;
+            } while (true);
+
+            return $next;
+
+        case self::RECUR_YEARLY_DATE:
+            // Start with the start date of the event.
+            $estart = clone $this->start;
+            $after = clone $after;
+
+            if ($after->month > $estart->month ||
+                ($after->month == $estart->month && $after->mday > $estart->mday)) {
+                ++$after->year;
+                $after->month = $estart->month;
+                $after->mday = $estart->mday;
+            }
+
+            // Seperate case here for February 29th
+            if ($estart->month == 2 && $estart->mday == 29) {
+                while (!Horde_Date_Utils::isLeapYear($after->year)) {
+                    ++$after->year;
+                }
+            }
+
+            // Adjust $estart to be the first candidate.
+            $offset = $after->year - $estart->year;
+            if ($offset > 0) {
+                $offset = floor(($offset + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
+                $estart->year += $offset;
+            }
+
+            // We've gone past the end of recurrence; give up.
+            if ($this->recurCount &&
+                $offset >= $this->recurCount) {
+                return false;
+            }
+            if ($this->hasRecurEnd() &&
+                $this->recurEnd->compareDateTime($estart) < 0) {
+                return false;
+            }
+
+            return $estart;
+
+        case self::RECUR_YEARLY_DAY:
+            // Check count first.
+            $dayofyear = $this->start->dayOfYear();
+            $count = ($after->year - $this->start->year) / $this->recurInterval + 1;
+            if ($this->recurCount &&
+                ($count > $this->recurCount ||
+                 ($count == $this->recurCount &&
+                  $after->dayOfYear() > $dayofyear))) {
+                return false;
+            }
+
+            // Start with a rough interval.
+            $estart = clone $this->start;
+            $estart->year += floor($count - 1) * $this->recurInterval;
+
+            // Now add the difference to the required day of year.
+            $estart->mday += $dayofyear - $estart->dayOfYear();
+
+            // Add an interval if the estimation was wrong.
+            if ($estart->compareDate($after) < 0) {
+                $estart->year += $this->recurInterval;
+                $estart->mday += $dayofyear - $estart->dayOfYear();
+            }
+
+            // We've gone past the end of recurrence; give up.
+            if ($this->hasRecurEnd() &&
+                $this->recurEnd->compareDateTime($estart) < 0) {
+                return false;
+            }
+
+            return $estart;
+
+        case self::RECUR_YEARLY_WEEKDAY:
+            // Start with the start date of the event.
+            $estart = clone $this->start;
+
+            // What day of the week, and week of the month, do we recur on?
+            $nth = ceil($this->start->mday / 7);
+            $weekday = $estart->dayOfWeek();
+
+            // Adjust $estart to be the first candidate.
+            $offset = floor(($after->year - $estart->year + $this->recurInterval - 1) / $this->recurInterval) * $this->recurInterval;
+
+            // Adjust our working date until it's after $after.
+            $estart->year += $offset - $this->recurInterval;
+
+            $count = $offset / $this->recurInterval;
+            do {
+                if ($this->recurCount &&
+                    $count++ >= $this->recurCount) {
+                    return false;
+                }
+
+                $estart->year += $this->recurInterval;
+
+                $next = clone $estart;
+                $next->setNthWeekday($weekday, $nth);
+
+                if ($next->compareDateTime($after) < 0) {
+                    // We haven't made it past $after yet, try again.
+                    continue;
+                }
+                if ($this->hasRecurEnd() &&
+                    $next->compareDateTime($this->recurEnd) > 0) {
+                    // We've gone past the end of recurrence; we can give up
+                    // now.
+                    return false;
+                }
+
+                // We have a candidate to return.
+                break;
+            } while (true);
+
+            return $next;
+        }
+
+        // We didn't find anything, the recurType was bad, or something else
+        // went wrong - return false.
+        return false;
+    }
+
+    /**
+     * Returns whether this event has any date that matches the recurrence
+     * rules and is not an exception.
+     *
+     * @return boolean  True if an active recurrence exists.
+     */
+    public function hasActiveRecurrence()
+    {
+        if (!$this->hasRecurEnd()) {
+            return true;
+        }
+
+        $next = $this->nextRecurrence(new Horde_Date($this->start));
+        while (is_object($next)) {
+            if (!$this->hasException($next->year, $next->month, $next->mday) &&
+                !$this->hasCompletion($next->year, $next->month, $next->mday)) {
+                return true;
+            }
+
+            $next = $this->nextRecurrence($next->add(array('day' => 1)));
+        }
+
+        return false;
+    }
+
+    /**
+     * Returns the next active recurrence.
+     *
+     * @param Horde_Date $afterDate  Return events after this date.
+     *
+     * @return Horde_Date|boolean The date of the next active
+     *                             recurrence or false if the event
+     *                             has no active recurrence after
+     *                             $afterDate.
+     */
+    public function nextActiveRecurrence($afterDate)
+    {
+        $next = $this->nextRecurrence($afterDate);
+        while (is_object($next)) {
+            if (!$this->hasException($next->year, $next->month, $next->mday) &&
+                !$this->hasCompletion($next->year, $next->month, $next->mday)) {
+                return $next;
+            }
+            $next->mday++;
+            $next = $this->nextRecurrence($next);
+        }
+
+        return false;
+    }
+
+    /**
+     * Adds an exception to a recurring event.
+     *
+     * @param integer $year   The year of the execption.
+     * @param integer $month  The month of the execption.
+     * @param integer $mday   The day of the month of the exception.
+     */
+    public function addException($year, $month, $mday)
+    {
+        $this->exceptions[] = sprintf('%04d%02d%02d', $year, $month, $mday);
+    }
+
+    /**
+     * Deletes an exception from a recurring event.
+     *
+     * @param integer $year   The year of the execption.
+     * @param integer $month  The month of the execption.
+     * @param integer $mday   The day of the month of the exception.
+     */
+    public function deleteException($year, $month, $mday)
+    {
+        $key = array_search(sprintf('%04d%02d%02d', $year, $month, $mday), $this->exceptions);
+        if ($key !== false) {
+            unset($this->exceptions[$key]);
+        }
+    }
+
+    /**
+     * Checks if an exception exists for a given reccurence of an event.
+     *
+     * @param integer $year   The year of the reucrance.
+     * @param integer $month  The month of the reucrance.
+     * @param integer $mday   The day of the month of the reucrance.
+     *
+     * @return boolean  True if an exception exists for the given date.
+     */
+    public function hasException($year, $month, $mday)
+    {
+        return in_array(sprintf('%04d%02d%02d', $year, $month, $mday),
+                        $this->getExceptions());
+    }
+
+    /**
+     * Retrieves all the exceptions for this event.
+     *
+     * @return array  Array containing the dates of all the exceptions in
+     *                YYYYMMDD form.
+     */
+    public function getExceptions()
+    {
+        return $this->exceptions;
+    }
+
+    /**
+     * Adds a completion to a recurring event.
+     *
+     * @param integer $year   The year of the execption.
+     * @param integer $month  The month of the execption.
+     * @param integer $mday   The day of the month of the completion.
+     */
+    public function addCompletion($year, $month, $mday)
+    {
+        $this->completions[] = sprintf('%04d%02d%02d', $year, $month, $mday);
+    }
+
+    /**
+     * Deletes a completion from a recurring event.
+     *
+     * @param integer $year   The year of the execption.
+     * @param integer $month  The month of the execption.
+     * @param integer $mday   The day of the month of the completion.
+     */
+    public function deleteCompletion($year, $month, $mday)
+    {
+        $key = array_search(sprintf('%04d%02d%02d', $year, $month, $mday), $this->completions);
+        if ($key !== false) {
+            unset($this->completions[$key]);
+        }
+    }
+
+    /**
+     * Checks if a completion exists for a given reccurence of an event.
+     *
+     * @param integer $year   The year of the reucrance.
+     * @param integer $month  The month of the recurrance.
+     * @param integer $mday   The day of the month of the recurrance.
+     *
+     * @return boolean  True if a completion exists for the given date.
+     */
+    public function hasCompletion($year, $month, $mday)
+    {
+        return in_array(sprintf('%04d%02d%02d', $year, $month, $mday),
+                        $this->getCompletions());
+    }
+
+    /**
+     * Retrieves all the completions for this event.
+     *
+     * @return array  Array containing the dates of all the completions in
+     *                YYYYMMDD form.
+     */
+    public function getCompletions()
+    {
+        return $this->completions;
+    }
+
+    /**
+     * Parses a vCalendar 1.0 recurrence rule.
+     *
+     * @link http://www.imc.org/pdi/vcal-10.txt
+     * @link http://www.shuchow.com/vCalAddendum.html
+     *
+     * @param string $rrule  A vCalendar 1.0 conform RRULE value.
+     */
+    public function fromRRule10($rrule)
+    {
+        $this->reset();
+
+        if (!$rrule) {
+            return;
+        }
+
+        if (!preg_match('/([A-Z]+)(\d+)?(.*)/', $rrule, $matches)) {
+            // No recurrence data - event does not recur.
+            $this->setRecurType(self::RECUR_NONE);
+        }
+
+        // Always default the recurInterval to 1.
+        $this->setRecurInterval(!empty($matches[2]) ? $matches[2] : 1);
+
+        $remainder = trim($matches[3]);
+
+        switch ($matches[1]) {
+        case 'D':
+            $this->setRecurType(self::RECUR_DAILY);
+            break;
+
+        case 'W':
+            $this->setRecurType(self::RECUR_WEEKLY);
+            if (!empty($remainder)) {
+                $maskdays = array(
+                    'SU' => Horde_Date::MASK_SUNDAY,
+                    'MO' => Horde_Date::MASK_MONDAY,
+                    'TU' => Horde_Date::MASK_TUESDAY,
+                    'WE' => Horde_Date::MASK_WEDNESDAY,
+                    'TH' => Horde_Date::MASK_THURSDAY,
+                    'FR' => Horde_Date::MASK_FRIDAY,
+                    'SA' => Horde_Date::MASK_SATURDAY,
+                );
+                $mask = 0;
+                while (preg_match('/^ ?[A-Z]{2} ?/', $remainder, $matches)) {
+                    $day = trim($matches[0]);
+                    $remainder = substr($remainder, strlen($matches[0]));
+                    $mask |= $maskdays[$day];
+                }
+                $this->setRecurOnDay($mask);
+            } else {
+                // Recur on the day of the week of the original recurrence.
+                $maskdays = array(
+                    Horde_Date::DATE_SUNDAY => Horde_Date::MASK_SUNDAY,
+                    Horde_Date::DATE_MONDAY => Horde_Date::MASK_MONDAY,
+                    Horde_Date::DATE_TUESDAY => Horde_Date::MASK_TUESDAY,
+                    Horde_Date::DATE_WEDNESDAY => Horde_Date::MASK_WEDNESDAY,
+                    Horde_Date::DATE_THURSDAY => Horde_Date::MASK_THURSDAY,
+                    Horde_Date::DATE_FRIDAY => Horde_Date::MASK_FRIDAY,
+                    Horde_Date::DATE_SATURDAY => Horde_Date::MASK_SATURDAY,
+                );
+                $this->setRecurOnDay($maskdays[$this->start->dayOfWeek()]);
+            }
+            break;
+
+        case 'MP':
+            $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
+            break;
+
+        case 'MD':
+            $this->setRecurType(self::RECUR_MONTHLY_DATE);
+            break;
+
+        case 'YM':
+            $this->setRecurType(self::RECUR_YEARLY_DATE);
+            break;
+
+        case 'YD':
+            $this->setRecurType(self::RECUR_YEARLY_DAY);
+            break;
+        }
+
+        // We don't support modifiers at the moment, strip them.
+        while ($remainder && !preg_match('/^(#\d+|\d{8})($| |T\d{6})/', $remainder)) {
+               $remainder = substr($remainder, 1);
+        }
+        if (!empty($remainder)) {
+            if (strpos($remainder, '#') === 0) {
+                $this->setRecurCount(substr($remainder, 1));
+            } else {
+                list($year, $month, $mday) = sscanf($remainder, '%04d%02d%02d');
+                $this->setRecurEnd(new Horde_Date(array('year' => $year,
+                                                        'month' => $month,
+                                                        'mday' => $mday)));
+            }
+        }
+    }
+
+    /**
+     * Creates a vCalendar 1.0 recurrence rule.
+     *
+     * @link http://www.imc.org/pdi/vcal-10.txt
+     * @link http://www.shuchow.com/vCalAddendum.html
+     *
+     * @param Horde_Icalendar $calendar  A Horde_Icalendar object instance.
+     *
+     * @return string  A vCalendar 1.0 conform RRULE value.
+     */
+    public function toRRule10($calendar)
+    {
+        switch ($this->recurType) {
+        case self::RECUR_NONE:
+            return '';
+
+        case self::RECUR_DAILY:
+            $rrule = 'D' . $this->recurInterval;
+            break;
+
+        case self::RECUR_WEEKLY:
+            $rrule = 'W' . $this->recurInterval;
+            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
+
+            for ($i = 0; $i <= 7; ++$i) {
+                if ($this->recurOnDay(pow(2, $i))) {
+                    $rrule .= ' ' . $vcaldays[$i];
+                }
+            }
+            break;
+
+        case self::RECUR_MONTHLY_DATE:
+            $rrule = 'MD' . $this->recurInterval . ' ' . trim($this->start->mday);
+            break;
+
+        case self::RECUR_MONTHLY_WEEKDAY:
+            $nth_weekday = (int)($this->start->mday / 7);
+            if (($this->start->mday % 7) > 0) {
+                $nth_weekday++;
+            }
+
+            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
+            $rrule = 'MP' . $this->recurInterval . ' ' . $nth_weekday . '+ ' . $vcaldays[$this->start->dayOfWeek()];
+
+            break;
+
+        case self::RECUR_YEARLY_DATE:
+            $rrule = 'YM' . $this->recurInterval . ' ' . trim($this->start->month);
+            break;
+
+        case self::RECUR_YEARLY_DAY:
+            $rrule = 'YD' . $this->recurInterval . ' ' . $this->start->dayOfYear();
+            break;
+
+        default:
+            return '';
+        }
+
+        if ($this->hasRecurEnd()) {
+            $recurEnd = clone $this->recurEnd;
+            return $rrule . ' ' . $calendar->_exportDateTime($recurEnd);
+        }
+
+        return $rrule . ' #' . (int)$this->getRecurCount();
+    }
+
+    /**
+     * Parses an iCalendar 2.0 recurrence rule.
+     *
+     * @link http://rfc.net/rfc2445.html#s4.3.10
+     * @link http://rfc.net/rfc2445.html#s4.8.5
+     * @link http://www.shuchow.com/vCalAddendum.html
+     *
+     * @param string $rrule  An iCalendar 2.0 conform RRULE value.
+     */
+    public function fromRRule20($rrule)
+    {
+        $this->reset();
+
+        // Parse the recurrence rule into keys and values.
+        $rdata = array();
+        $parts = explode(';', $rrule);
+        foreach ($parts as $part) {
+            list($key, $value) = explode('=', $part, 2);
+            $rdata[strtoupper($key)] = $value;
+        }
+
+        if (isset($rdata['FREQ'])) {
+            // Always default the recurInterval to 1.
+            $this->setRecurInterval(isset($rdata['INTERVAL']) ? $rdata['INTERVAL'] : 1);
+
+            switch (strtoupper($rdata['FREQ'])) {
+            case 'DAILY':
+                $this->setRecurType(self::RECUR_DAILY);
+                break;
+
+            case 'WEEKLY':
+                $this->setRecurType(self::RECUR_WEEKLY);
+                if (isset($rdata['BYDAY'])) {
+                    $maskdays = array(
+                        'SU' => Horde_Date::MASK_SUNDAY,
+                        'MO' => Horde_Date::MASK_MONDAY,
+                        'TU' => Horde_Date::MASK_TUESDAY,
+                        'WE' => Horde_Date::MASK_WEDNESDAY,
+                        'TH' => Horde_Date::MASK_THURSDAY,
+                        'FR' => Horde_Date::MASK_FRIDAY,
+                        'SA' => Horde_Date::MASK_SATURDAY,
+                    );
+                    $days = explode(',', $rdata['BYDAY']);
+                    $mask = 0;
+                    foreach ($days as $day) {
+                        $mask |= $maskdays[$day];
+                    }
+                    $this->setRecurOnDay($mask);
+                } else {
+                    // Recur on the day of the week of the original
+                    // recurrence.
+                    $maskdays = array(
+                        Horde_Date::DATE_SUNDAY => Horde_Date::MASK_SUNDAY,
+                        Horde_Date::DATE_MONDAY => Horde_Date::MASK_MONDAY,
+                        Horde_Date::DATE_TUESDAY => Horde_Date::MASK_TUESDAY,
+                        Horde_Date::DATE_WEDNESDAY => Horde_Date::MASK_WEDNESDAY,
+                        Horde_Date::DATE_THURSDAY => Horde_Date::MASK_THURSDAY,
+                        Horde_Date::DATE_FRIDAY => Horde_Date::MASK_FRIDAY,
+                        Horde_Date::DATE_SATURDAY => Horde_Date::MASK_SATURDAY);
+                    $this->setRecurOnDay($maskdays[$this->start->dayOfWeek()]);
+                }
+                break;
+
+            case 'MONTHLY':
+                if (isset($rdata['BYDAY'])) {
+                    $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
+                } else {
+                    $this->setRecurType(self::RECUR_MONTHLY_DATE);
+                }
+                break;
+
+            case 'YEARLY':
+                if (isset($rdata['BYYEARDAY'])) {
+                    $this->setRecurType(self::RECUR_YEARLY_DAY);
+                } elseif (isset($rdata['BYDAY'])) {
+                    $this->setRecurType(self::RECUR_YEARLY_WEEKDAY);
+                } else {
+                    $this->setRecurType(self::RECUR_YEARLY_DATE);
+                }
+                break;
+            }
+
+            if (isset($rdata['UNTIL'])) {
+                list($year, $month, $mday) = sscanf($rdata['UNTIL'],
+                                                    '%04d%02d%02d');
+                $this->setRecurEnd(new Horde_Date(array('year' => $year,
+                                                        'month' => $month,
+                                                        'mday' => $mday)));
+            }
+            if (isset($rdata['COUNT'])) {
+                $this->setRecurCount($rdata['COUNT']);
+            }
+        } else {
+            // No recurrence data - event does not recur.
+            $this->setRecurType(self::RECUR_NONE);
+        }
+    }
+
+    /**
+     * Creates an iCalendar 2.0 recurrence rule.
+     *
+     * @link http://rfc.net/rfc2445.html#s4.3.10
+     * @link http://rfc.net/rfc2445.html#s4.8.5
+     * @link http://www.shuchow.com/vCalAddendum.html
+     *
+     * @param Horde_Icalendar $calendar  A Horde_Icalendar object instance.
+     *
+     * @return string  An iCalendar 2.0 conform RRULE value.
+     */
+    public function toRRule20($calendar)
+    {
+        switch ($this->recurType) {
+        case self::RECUR_NONE:
+            return '';
+
+        case self::RECUR_DAILY:
+            $rrule = 'FREQ=DAILY;INTERVAL='  . $this->recurInterval;
+            break;
+
+        case self::RECUR_WEEKLY:
+            $rrule = 'FREQ=WEEKLY;INTERVAL=' . $this->recurInterval . ';BYDAY=';
+            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
+
+            for ($i = $flag = 0; $i <= 7; ++$i) {
+                if ($this->recurOnDay(pow(2, $i))) {
+                    if ($flag) {
+                        $rrule .= ',';
+                    }
+                    $rrule .= $vcaldays[$i];
+                    $flag = true;
+                }
+            }
+            break;
+
+        case self::RECUR_MONTHLY_DATE:
+            $rrule = 'FREQ=MONTHLY;INTERVAL=' . $this->recurInterval;
+            break;
+
+        case self::RECUR_MONTHLY_WEEKDAY:
+            $nth_weekday = (int)($this->start->mday / 7);
+            if (($this->start->mday % 7) > 0) {
+                $nth_weekday++;
+            }
+            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
+            $rrule = 'FREQ=MONTHLY;INTERVAL=' . $this->recurInterval
+                . ';BYDAY=' . $nth_weekday . $vcaldays[$this->start->dayOfWeek()];
+            break;
+
+        case self::RECUR_YEARLY_DATE:
+            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval;
+            break;
+
+        case self::RECUR_YEARLY_DAY:
+            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval
+                . ';BYYEARDAY=' . $this->start->dayOfYear();
+            break;
+
+        case self::RECUR_YEARLY_WEEKDAY:
+            $nth_weekday = (int)($this->start->mday / 7);
+            if (($this->start->mday % 7) > 0) {
+                $nth_weekday++;
+            }
+            $vcaldays = array('SU', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA');
+            $rrule = 'FREQ=YEARLY;INTERVAL=' . $this->recurInterval
+                . ';BYDAY='
+                . $nth_weekday
+                . $vcaldays[$this->start->dayOfWeek()]
+                . ';BYMONTH=' . $this->start->month;
+            break;
+        }
+
+        if ($this->hasRecurEnd()) {
+            $recurEnd = clone $this->recurEnd;
+            $rrule .= ';UNTIL=' . $calendar->_exportDateTime($recurEnd);
+        }
+        if ($count = $this->getRecurCount()) {
+            $rrule .= ';COUNT=' . $count;
+        }
+        return $rrule;
+    }
+
+    /**
+     * Parses the recurrence data from a hash.
+     *
+     * @param array $hash  The hash to convert.
+     *
+     * @return boolean  True if the hash seemed valid, false otherwise.
+     */
+    public function fromHash($hash)
+    {
+        $this->reset();
+
+        if (!isset($hash['interval']) || !isset($hash['cycle'])) {
+            $this->setRecurType(self::RECUR_NONE);
+            return false;
+        }
+
+        $this->setRecurInterval((int)$hash['interval']);
+
+        $parse_day = false;
+        $set_daymask = false;
+        $update_month = false;
+        $update_daynumber = false;
+        $update_weekday = false;
+        $nth_weekday = -1;
+
+        switch ($hash['cycle']) {
+        case 'daily':
+            $this->setRecurType(self::RECUR_DAILY);
+            break;
+
+        case 'weekly':
+            $this->setRecurType(self::RECUR_WEEKLY);
+            $parse_day = true;
+            $set_daymask = true;
+            break;
+
+        case 'monthly':
+            if (!isset($hash['daynumber'])) {
+                $this->setRecurType(self::RECUR_NONE);
+                return false;
+            }
+
+            switch ($hash['type']) {
+            case 'daynumber':
+                $this->setRecurType(self::RECUR_MONTHLY_DATE);
+                $update_daynumber = true;
+                break;
+
+            case 'weekday':
+                $this->setRecurType(self::RECUR_MONTHLY_WEEKDAY);
+                $nth_weekday = (int)$hash['daynumber'];
+                $hash['daynumber'] = 1;
+                $parse_day = true;
+                $update_daynumber = true;
+                $update_weekday = true;
+                break;
+            }
+            break;
+
+        case 'yearly':
+            if (!isset($hash['type'])) {
+                $this->setRecurType(self::RECUR_NONE);
+                return false;
+            }
+
+            switch ($hash['type']) {
+            case 'monthday':
+                $this->setRecurType(self::RECUR_YEARLY_DATE);
+                $update_month = true;
+                $update_daynumber = true;
+                break;
+
+            case 'yearday':
+                if (!isset($hash['month'])) {
+                    $this->setRecurType(self::RECUR_NONE);
+                    return false;
+                }
+
+                $this->setRecurType(self::RECUR_YEARLY_DAY);
+                // Start counting days in January.
+                $hash['month'] = 'january';
+                $update_month = true;
+                $update_daynumber = true;
+                break;
+
+            case 'weekday':
+                if (!isset($hash['daynumber'])) {
+                    $this->setRecurType(self::RECUR_NONE);
+                    return false;
+                }
+
+                $this->setRecurType(self::RECUR_YEARLY_WEEKDAY);
+                $nth_weekday = (int)$hash['daynumber'];
+                $hash['daynumber'] = 1;
+                $parse_day = true;
+                $update_month = true;
+                $update_daynumber = true;
+                $update_weekday = true;
+                break;
+            }
+        }
+
+        if (isset($hash['range-type']) && isset($hash['range'])) {
+            switch ($hash['range-type']) {
+            case 'number':
+                $this->setRecurCount((int)$hash['range']);
+                break;
+
+            case 'date':
+                $recur_end = new Horde_Date($hash['range']);
+                $recur_end->hour = 23;
+                $recur_end->min = 59;
+                $recur_end->sec = 59;
+                $this->setRecurEnd($recur_end);
+                break;
+            }
+        }
+
+        // Need to parse <day>?
+        $last_found_day = -1;
+        if ($parse_day) {
+            if (!isset($hash['day'])) {
+                $this->setRecurType(self::RECUR_NONE);
+                return false;
+            }
+
+            $mask = 0;
+            $bits = array(
+                'monday' => Horde_Date::MASK_MONDAY,
+                'tuesday' => Horde_Date::MASK_TUESDAY,
+                'wednesday' => Horde_Date::MASK_WEDNESDAY,
+                'thursday' => Horde_Date::MASK_THURSDAY,
+                'friday' => Horde_Date::MASK_FRIDAY,
+                'saturday' => Horde_Date::MASK_SATURDAY,
+                'sunday' => Horde_Date::MASK_SUNDAY,
+            );
+            $days = array(
+                'monday' => Horde_Date::DATE_MONDAY,
+                'tuesday' => Horde_Date::DATE_TUESDAY,
+                'wednesday' => Horde_Date::DATE_WEDNESDAY,
+                'thursday' => Horde_Date::DATE_THURSDAY,
+                'friday' => Horde_Date::DATE_FRIDAY,
+                'saturday' => Horde_Date::DATE_SATURDAY,
+                'sunday' => Horde_Date::DATE_SUNDAY,
+            );
+
+            foreach ($hash['day'] as $day) {
+                // Validity check.
+                if (empty($day) || !isset($bits[$day])) {
+                    continue;
+                }
+
+                $mask |= $bits[$day];
+                $last_found_day = $days[$day];
+            }
+
+            if ($set_daymask) {
+                $this->setRecurOnDay($mask);
+            }
+        }
+
+        if ($update_month || $update_daynumber || $update_weekday) {
+            if ($update_month) {
+                $month2number = array(
+                    'january'   => 1,
+                    'february'  => 2,
+                    'march'     => 3,
+                    'april'     => 4,
+                    'may'       => 5,
+                    'june'      => 6,
+                    'july'      => 7,
+                    'august'    => 8,
+                    'september' => 9,
+                    'october'   => 10,
+                    'november'  => 11,
+                    'december'  => 12,
+                );
+
+                if (isset($month2number[$hash['month']])) {
+                    $this->start->month = $month2number[$hash['month']];
+                }
+            }
+
+            if ($update_daynumber) {
+                if (!isset($hash['daynumber'])) {
+                    $this->setRecurType(self::RECUR_NONE);
+                    return false;
+                }
+
+                $this->start->mday = $hash['daynumber'];
+            }
+
+            if ($update_weekday) {
+                $this->start->setNthWeekday($last_found_day, $nth_weekday);
+            }
+        }
+
+        // Exceptions.
+        if (isset($hash['exceptions'])) {
+            $this->exceptions = $hash['exceptions'];
+        }
+
+        if (isset($hash['completions'])) {
+            $this->completions = $hash['completions'];
+        }
+
+        return true;
+    }
+
+    /**
+     * Export this object into a hash.
+     *
+     * @return array  The recurrence hash.
+     */
+    public function toHash()
+    {
+        if ($this->getRecurType() == self::RECUR_NONE) {
+            return array();
+        }
+
+        $day2number = array(
+            0 => 'sunday',
+            1 => 'monday',
+            2 => 'tuesday',
+            3 => 'wednesday',
+            4 => 'thursday',
+            5 => 'friday',
+            6 => 'saturday'
+        );
+        $month2number = array(
+            1 => 'january',
+            2 => 'february',
+            3 => 'march',
+            4 => 'april',
+            5 => 'may',
+            6 => 'june',
+            7 => 'july',
+            8 => 'august',
+            9 => 'september',
+            10 => 'october',
+            11 => 'november',
+            12 => 'december'
+        );
+
+        $hash = array('interval' => $this->getRecurInterval());
+        $start = $this->getRecurStart();
+
+        switch ($this->getRecurType()) {
+        case self::RECUR_DAILY:
+            $hash['cycle'] = 'daily';
+            break;
+
+        case self::RECUR_WEEKLY:
+            $hash['cycle'] = 'weekly';
+            $bits = array(
+                'monday' => Horde_Date::MASK_MONDAY,
+                'tuesday' => Horde_Date::MASK_TUESDAY,
+                'wednesday' => Horde_Date::MASK_WEDNESDAY,
+                'thursday' => Horde_Date::MASK_THURSDAY,
+                'friday' => Horde_Date::MASK_FRIDAY,
+                'saturday' => Horde_Date::MASK_SATURDAY,
+                'sunday' => Horde_Date::MASK_SUNDAY,
+            );
+            $days = array();
+            foreach ($bits as $name => $bit) {
+                if ($this->recurOnDay($bit)) {
+                    $days[] = $name;
+                }
+            }
+            $hash['day'] = $days;
+            break;
+
+        case self::RECUR_MONTHLY_DATE:
+            $hash['cycle'] = 'monthly';
+            $hash['type'] = 'daynumber';
+            $hash['daynumber'] = $start->mday;
+            break;
+
+        case self::RECUR_MONTHLY_WEEKDAY:
+            $hash['cycle'] = 'monthly';
+            $hash['type'] = 'weekday';
+            $hash['daynumber'] = $start->weekOfMonth();
+            $hash['day'] = array ($day2number[$start->dayOfWeek()]);
+            break;
+
+        case self::RECUR_YEARLY_DATE:
+            $hash['cycle'] = 'yearly';
+            $hash['type'] = 'monthday';
+            $hash['daynumber'] = $start->mday;
+            $hash['month'] = $month2number[$start->month];
+            break;
+
+        case self::RECUR_YEARLY_DAY:
+            $hash['cycle'] = 'yearly';
+            $hash['type'] = 'yearday';
+            $hash['daynumber'] = $start->dayOfYear();
+            break;
+
+        case self::RECUR_YEARLY_WEEKDAY:
+            $hash['cycle'] = 'yearly';
+            $hash['type'] = 'weekday';
+            $hash['daynumber'] = $start->weekOfMonth();
+            $hash['day'] = array ($day2number[$start->dayOfWeek()]);
+            $hash['month'] = $month2number[$start->month];
+        }
+
+        if ($this->hasRecurCount()) {
+            $hash['range-type'] = 'number';
+            $hash['range'] = $this->getRecurCount();
+        } elseif ($this->hasRecurEnd()) {
+            $date = $this->getRecurEnd();
+            $hash['range-type'] = 'date';
+            $hash['range'] = $date->datestamp();
+        } else {
+            $hash['range-type'] = 'none';
+            $hash['range'] = '';
+        }
+
+        // Recurrence exceptions
+        $hash['exceptions'] = $this->exceptions;
+        $hash['completions'] = $this->completions;
+
+        return $hash;
+    }
+
+    /**
+     * Returns a simple object suitable for json transport representing this
+     * object.
+     *
+     * Possible properties are:
+     * - t: type
+     * - i: interval
+     * - e: end date
+     * - c: count
+     * - d: data
+     * - co: completions
+     * - ex: exceptions
+     *
+     * @return object  A simple object.
+     */
+    public function toJson()
+    {
+        $json = new stdClass;
+        $json->t = $this->recurType;
+        $json->i = $this->recurInterval;
+        if ($this->hasRecurEnd()) {
+            $json->e = $this->recurEnd->toJson();
+        }
+        if ($this->recurCount) {
+            $json->c = $this->recurCount;
+        }
+        if ($this->recurData) {
+            $json->d = $this->recurData;
+        }
+        if ($this->completions) {
+            $json->co = $this->completions;
+        }
+        if ($this->exceptions) {
+            $json->ex = $this->exceptions;
+        }
+        return $json;
+    }
+
+}
+
+
diff --git a/plugins/libkolab/lib/kolab_date_recurrence.php b/plugins/libkolab/lib/kolab_date_recurrence.php
new file mode 100644
index 0000000..c840864
--- /dev/null
+++ b/plugins/libkolab/lib/kolab_date_recurrence.php
@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * Recurrence computation class for xcal-based Kolab format objects
+ *
+ * Uitility class to compute instances of recurring events.
+ *
+ * @version @package_version@
+ * @author Thomas Bruederli <bruederli at kolabsys.com>
+ *
+ * Copyright (C) 2012, Kolab Systems AG <contact at 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 kolab_date_recurrence
+{
+  private $engine;
+  private $tz_offset = 0;
+  private $allday = false;
+  private $hour = 0;
+
+  /**
+   * Default constructor
+   *
+   * @param array The Kolab object to operate on
+   */
+  function __construct($object)
+  {
+      // use (copied) Horde classes to compute recurring instances
+      // TODO: replace with something that has less than 6'000 lines of code
+      $this->engine = new Horde_Date_Recurrence($object['start']);
+      $this->engine->fromRRule20($this->to_rrule($object['recurrence']));  // TODO: get that string directly from libkolabxml
+
+      foreach ((array)$object['recurrence']['EXDATE'] as $exdate)
+          $this->engine->addException(date('Y', $exdate), date('n', $exdate), date('j', $exdate));
+
+      $now = new DateTime('now', kolab_format::$timezone);
+      $this->tz_offset = $object['allday'] ? $now->getOffset() - date('Z') : 0;
+      $this->next = new Horde_Date($object['start'] + $this->tz_offset);  # shift all-day times to server timezone because computation operates in local TZ
+      $this->dst_start = $this->next->format('I');
+      $this->allday = $object['allday'];
+      $this->hour = $this->next->hour;
+  }
+
+  /**
+   * Get timestamp of the next occurence of this event
+   *
+   * @return mixed Unix timestamp or False if recurrence ended
+   */
+  public function next_start()
+  {
+    $time = false;
+    if ($this->next && ($next = $this->engine->nextActiveRecurrence(array('year' => $this->next->year, 'month' => $this->next->month, 'mday' => $this->next->mday + 1, 'hour' => $this->next->hour, 'min' => $this->next->min, 'sec' => $this->next->sec)))) {
+      if ($this->allday) {
+        $next->hour = $this->hour;  # fix time for all-day events
+        $next->min = 0;
+      }
+      # consider difference in daylight saving between base event and recurring instance
+      $dst_diff = ($this->dst_start - $next->format('I')) * 3600;
+      $time = $next->timestamp() - $this->tz_offset - $dst_diff;
+      $this->next = $next;
+    }
+
+    return $time;
+  }
+
+  /**
+   * Convert the internal structured data into a vcalendar RRULE 2.0 string
+   */
+  private function to_rrule($recurrence)
+  {
+    if (is_string($recurrence))
+        return $recurrence;
+
+      $rrule = '';
+      foreach ((array)$recurrence as $k => $val) {
+          $k = strtoupper($k);
+          switch ($k) {
+          case 'UNTIL':
+              $val = gmdate('Ymd\THis', $val);
+              break;
+          case 'EXDATE':
+              foreach ((array)$val as $i => $ex)
+                  $val[$i] = gmdate('Ymd\THis', $ex);
+              $val = join(',', (array)$val);
+              break;
+          }
+          $rrule .= $k . '=' . $val . ';';
+      }
+
+    return $rrule;
+  }
+
+}





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