--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/libcalendaring/lib/Sabre/VObject/RecurrenceIterator.php	Sat Jan 13 08:57:56 2018 -0500
@@ -0,0 +1,1144 @@
+<?php
+
+namespace Sabre\VObject;
+
+/**
+ * This class is used to determine new for a recurring event, when the next
+ * events occur.
+ *
+ * This iterator may loop infinitely in the future, therefore it is important
+ * that if you use this class, you set hard limits for the amount of iterations
+ * you want to handle.
+ *
+ * Note that currently there is not full support for the entire iCalendar
+ * specification, as it's very complex and contains a lot of permutations
+ * that's not yet used very often in software.
+ *
+ * For the focus has been on features as they actually appear in Calendaring
+ * software, but this may well get expanded as needed / on demand
+ *
+ * The following RRULE properties are supported
+ *   * UNTIL
+ *   * INTERVAL
+ *   * COUNT
+ *   * FREQ=DAILY
+ *     * BYDAY
+ *     * BYHOUR
+ *   * FREQ=WEEKLY
+ *     * BYDAY
+ *     * BYHOUR
+ *     * WKST
+ *   * FREQ=MONTHLY
+ *     * BYMONTHDAY
+ *     * BYDAY
+ *     * BYSETPOS
+ *   * FREQ=YEARLY
+ *     * BYMONTH
+ *     * BYMONTHDAY (only if BYMONTH is also set)
+ *     * BYDAY (only if BYMONTH is also set)
+ *
+ * Anything beyond this is 'undefined', which means that it may get ignored, or
+ * you may get unexpected results. The effect is that in some applications the
+ * specified recurrence may look incorrect, or is missing.
+ *
+ * @copyright Copyright (C) 2007-2013 fruux GmbH (https://fruux.com/).
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class RecurrenceIterator implements \Iterator {
+
+    /**
+     * The initial event date
+     *
+     * @var DateTime
+     */
+    public $startDate;
+
+    /**
+     * The end-date of the initial event
+     *
+     * @var DateTime
+     */
+    public $endDate;
+
+    /**
+     * The 'current' recurrence.
+     *
+     * This will be increased for every iteration.
+     *
+     * @var DateTime
+     */
+    public $currentDate;
+
+
+    /**
+     * List of dates that are excluded from the rules.
+     *
+     * This list contains the items that have been overriden by the EXDATE
+     * property.
+     *
+     * @var array
+     */
+    public $exceptionDates = array();
+
+    /**
+     * Base event
+     *
+     * @var Component\VEvent
+     */
+    public $baseEvent;
+
+    /**
+     * List of dates that are overridden by other events.
+     * Similar to $overriddenEvents, but this just contains the original dates.
+     *
+     * @var array
+     */
+    public $overriddenDates = array();
+
+    /**
+     * list of events that are 'overridden'.
+     *
+     * This is an array of Component\VEvent objects.
+     *
+     * @var array
+     */
+    public $overriddenEvents = array();
+
+    /**
+     * Frequency is one of: secondly, minutely, hourly, daily, weekly, monthly,
+     * yearly.
+     *
+     * @var string
+     */
+    public $frequency;
+
+    /**
+     * The last instance of this recurrence, inclusively
+     *
+     * @var DateTime|null
+     */
+    public $until;
+
+    /**
+     * The number of recurrences, or 'null' if infinitely recurring.
+     *
+     * @var int
+     */
+    public $count;
+
+    /**
+     * The interval.
+     *
+     * If for example frequency is set to daily, interval = 2 would mean every
+     * 2 days.
+     *
+     * @var int
+     */
+    public $interval = 1;
+
+    /**
+     * Which seconds to recur.
+     *
+     * This is an array of integers (between 0 and 60)
+     *
+     * @var array
+     */
+    public $bySecond;
+
+    /**
+     * Which minutes to recur
+     *
+     * This is an array of integers (between 0 and 59)
+     *
+     * @var array
+     */
+    public $byMinute;
+
+    /**
+     * Which hours to recur
+     *
+     * This is an array of integers (between 0 and 23)
+     *
+     * @var array
+     */
+    public $byHour;
+
+    /**
+     * Which weekdays to recur.
+     *
+     * This is an array of weekdays
+     *
+     * This may also be preceeded by a positive or negative integer. If present,
+     * this indicates the nth occurrence of a specific day within the monthly or
+     * yearly rrule. For instance, -2TU indicates the second-last tuesday of
+     * the month, or year.
+     *
+     * @var array
+     */
+    public $byDay;
+
+    /**
+     * Which days of the month to recur
+     *
+     * This is an array of days of the months (1-31). The value can also be
+     * negative. -5 for instance means the 5th last day of the month.
+     *
+     * @var array
+     */
+    public $byMonthDay;
+
+    /**
+     * Which days of the year to recur.
+     *
+     * This is an array with days of the year (1 to 366). The values can also
+     * be negative. For instance, -1 will always represent the last day of the
+     * year. (December 31st).
+     *
+     * @var array
+     */
+    public $byYearDay;
+
+    /**
+     * Which week numbers to recur.
+     *
+     * This is an array of integers from 1 to 53. The values can also be
+     * negative. -1 will always refer to the last week of the year.
+     *
+     * @var array
+     */
+    public $byWeekNo;
+
+    /**
+     * Which months to recur
+     *
+     * This is an array of integers from 1 to 12.
+     *
+     * @var array
+     */
+    public $byMonth;
+
+    /**
+     * Which items in an existing st to recur.
+     *
+     * These numbers work together with an existing by* rule. It specifies
+     * exactly which items of the existing by-rule to filter.
+     *
+     * Valid values are 1 to 366 and -1 to -366. As an example, this can be
+     * used to recur the last workday of the month.
+     *
+     * This would be done by setting frequency to 'monthly', byDay to
+     * 'MO,TU,WE,TH,FR' and bySetPos to -1.
+     *
+     * @var array
+     */
+    public $bySetPos;
+
+    /**
+     * When a week starts
+     *
+     * @var string
+     */
+    public $weekStart = 'MO';
+
+    /**
+     * The current item in the list
+     *
+     * @var int
+     */
+    public $counter = 0;
+
+    /**
+     * Simple mapping from iCalendar day names to day numbers
+     *
+     * @var array
+     */
+    private $dayMap = array(
+        'SU' => 0,
+        'MO' => 1,
+        'TU' => 2,
+        'WE' => 3,
+        'TH' => 4,
+        'FR' => 5,
+        'SA' => 6,
+    );
+
+    /**
+     * Mappings between the day number and english day name.
+     *
+     * @var array
+     */
+    private $dayNames = array(
+        0 => 'Sunday',
+        1 => 'Monday',
+        2 => 'Tuesday',
+        3 => 'Wednesday',
+        4 => 'Thursday',
+        5 => 'Friday',
+        6 => 'Saturday',
+    );
+
+    /**
+     * If the current iteration of the event is an overriden event, this
+     * property will hold the VObject
+     *
+     * @var Component
+     */
+    private $currentOverriddenEvent;
+
+    /**
+     * This property may contain the date of the next not-overridden event.
+     * This date is calculated sometimes a bit early, before overridden events
+     * are evaluated.
+     *
+     * @var DateTime
+     */
+    private $nextDate;
+
+    /**
+     * This counts the number of overridden events we've handled so far
+     *
+     * @var int
+     */
+    private $handledOverridden = 0;
+
+    /**
+     * Creates the iterator
+     *
+     * You should pass a VCALENDAR component, as well as the UID of the event
+     * we're going to traverse.
+     *
+     * @param Component $vcal
+     * @param string|null $uid
+     */
+    public function __construct(Component $vcal, $uid=null) {
+
+        if (is_null($uid)) {
+            if ($vcal->name === 'VCALENDAR') {
+                throw new \InvalidArgumentException('If you pass a VCALENDAR object, you must pass a uid argument as well');
+            }
+            $components = array($vcal);
+            $uid = (string)$vcal->uid;
+        } else {
+            $components = $vcal->select('VEVENT');
+        }
+        foreach($components as $component) {
+            if ((string)$component->uid == $uid) {
+                if (isset($component->{'RECURRENCE-ID'})) {
+                    $this->overriddenEvents[$component->DTSTART->getDateTime()->getTimeStamp()] = $component;
+                    $this->overriddenDates[] = $component->{'RECURRENCE-ID'}->getDateTime();
+                } else {
+                    $this->baseEvent = $component;
+                }
+            }
+        }
+
+        ksort($this->overriddenEvents);
+
+        if (!$this->baseEvent) {
+            throw new \InvalidArgumentException('Could not find a base event with uid: ' . $uid);
+        }
+
+        $this->startDate = clone $this->baseEvent->DTSTART->getDateTime();
+
+        $this->endDate = null;
+        if (isset($this->baseEvent->DTEND)) {
+            $this->endDate = clone $this->baseEvent->DTEND->getDateTime();
+        } else {
+            $this->endDate = clone $this->startDate;
+            if (isset($this->baseEvent->DURATION)) {
+                $this->endDate->add(DateTimeParser::parse($this->baseEvent->DURATION->value));
+            } elseif ($this->baseEvent->DTSTART->getDateType()===Property\DateTime::DATE) {
+                $this->endDate->modify('+1 day');
+            }
+        }
+        $this->currentDate = clone $this->startDate;
+
+        $rrule = (string)$this->baseEvent->RRULE;
+
+        $parts = explode(';', $rrule);
+
+        // If no rrule was specified, we create a default setting
+        if (!$rrule) {
+            $this->frequency = 'daily';
+            $this->count = 1;
+        } else foreach($parts as $part) {
+
+            list($key, $value) = explode('=', $part, 2);
+
+            switch(strtoupper($key)) {
+
+                case 'FREQ' :
+                    if (!in_array(
+                        strtolower($value),
+                        array('secondly','minutely','hourly','daily','weekly','monthly','yearly')
+                    )) {
+                        throw new \InvalidArgumentException('Unknown value for FREQ=' . strtoupper($value));
+
+                    }
+                    $this->frequency = strtolower($value);
+                    break;
+
+                case 'UNTIL' :
+                    $this->until = DateTimeParser::parse($value);
+
+                    // In some cases events are generated with an UNTIL=
+                    // parameter before the actual start of the event.
+                    //
+                    // Not sure why this is happening. We assume that the
+                    // intention was that the event only recurs once.
+                    //
+                    // So we are modifying the parameter so our code doesn't
+                    // break.
+                    if($this->until < $this->baseEvent->DTSTART->getDateTime()) {
+                        $this->until = $this->baseEvent->DTSTART->getDateTime();
+                    }
+                    break;
+
+                case 'COUNT' :
+                    $this->count = (int)$value;
+                    break;
+
+                case 'INTERVAL' :
+                    $this->interval = (int)$value;
+                    if ($this->interval < 1) {
+                        throw new \InvalidArgumentException('INTERVAL in RRULE must be a positive integer!');
+                    }
+                    break;
+
+                case 'BYSECOND' :
+                    $this->bySecond = explode(',', $value);
+                    break;
+
+                case 'BYMINUTE' :
+                    $this->byMinute = explode(',', $value);
+                    break;
+
+                case 'BYHOUR' :
+                    $this->byHour = explode(',', $value);
+                    break;
+
+                case 'BYDAY' :
+                    $this->byDay = explode(',', strtoupper($value));
+                    break;
+
+                case 'BYMONTHDAY' :
+                    $this->byMonthDay = explode(',', $value);
+                    break;
+
+                case 'BYYEARDAY' :
+                    $this->byYearDay = explode(',', $value);
+                    break;
+
+                case 'BYWEEKNO' :
+                    $this->byWeekNo = explode(',', $value);
+                    break;
+
+                case 'BYMONTH' :
+                    $this->byMonth = explode(',', $value);
+                    break;
+
+                case 'BYSETPOS' :
+                    $this->bySetPos = explode(',', $value);
+                    break;
+
+                case 'WKST' :
+                    $this->weekStart = strtoupper($value);
+                    break;
+
+            }
+
+        }
+
+        // Parsing exception dates
+        if (isset($this->baseEvent->EXDATE)) {
+            foreach($this->baseEvent->EXDATE as $exDate) {
+
+                foreach(explode(',', (string)$exDate) as $exceptionDate) {
+
+                    $this->exceptionDates[] =
+                        DateTimeParser::parse($exceptionDate, $this->startDate->getTimeZone());
+
+                }
+
+            }
+
+        }
+
+    }
+
+    /**
+     * Returns the current item in the list
+     *
+     * @return DateTime
+     */
+    public function current() {
+
+        if (!$this->valid()) return null;
+        return clone $this->currentDate;
+
+    }
+
+    /**
+     * This method returns the startdate for the current iteration of the
+     * event.
+     *
+     * @return DateTime
+     */
+    public function getDtStart() {
+
+        if (!$this->valid()) return null;
+        return clone $this->currentDate;
+
+    }
+
+    /**
+     * This method returns the enddate for the current iteration of the
+     * event.
+     *
+     * @return DateTime
+     */
+    public function getDtEnd() {
+
+        if (!$this->valid()) return null;
+        $dtEnd = clone $this->currentDate;
+        $dtEnd->add( $this->startDate->diff( $this->endDate ) );
+        return clone $dtEnd;
+
+    }
+
+    /**
+     * Returns a VEVENT object with the updated start and end date.
+     *
+     * Any recurrence information is removed, and this function may return an
+     * 'overridden' event instead.
+     *
+     * This method always returns a cloned instance.
+     *
+     * @return Component\VEvent
+     */
+    public function getEventObject() {
+
+        if ($this->currentOverriddenEvent) {
+            return clone $this->currentOverriddenEvent;
+        }
+        $event = clone $this->baseEvent;
+        unset($event->RRULE);
+        unset($event->EXDATE);
+        unset($event->RDATE);
+        unset($event->EXRULE);
+
+        $event->DTSTART->setDateTime($this->getDTStart(), $event->DTSTART->getDateType());
+        if (isset($event->DTEND)) {
+            $event->DTEND->setDateTime($this->getDtEnd(), $event->DTSTART->getDateType());
+        }
+        if ($this->counter > 0) {
+            $event->{'RECURRENCE-ID'} = (string)$event->DTSTART;
+        }
+
+        return $event;
+
+    }
+
+    /**
+     * Returns the current item number
+     *
+     * @return int
+     */
+    public function key() {
+
+        return $this->counter;
+
+    }
+
+    /**
+     * Whether or not there is a 'next item'
+     *
+     * @return bool
+     */
+    public function valid() {
+
+        if (!is_null($this->count)) {
+            return $this->counter < $this->count;
+        }
+        if (!is_null($this->until) && $this->currentDate > $this->until) {
+
+            // Need to make sure there's no overridden events past the
+            // until date.
+            foreach($this->overriddenEvents as $overriddenEvent) {
+
+                if ($overriddenEvent->DTSTART->getDateTime() >= $this->currentDate) {
+
+                    return true;
+                }
+            }
+            return false;
+        }
+        return true;
+
+    }
+
+    /**
+     * Resets the iterator
+     *
+     * @return void
+     */
+    public function rewind() {
+
+        $this->currentDate = clone $this->startDate;
+        $this->counter = 0;
+
+    }
+
+    /**
+     * This method allows you to quickly go to the next occurrence after the
+     * specified date.
+     *
+     * Note that this checks the current 'endDate', not the 'stardDate'. This
+     * means that if you forward to January 1st, the iterator will stop at the
+     * first event that ends *after* January 1st.
+     *
+     * @param DateTime $dt
+     * @return void
+     */
+    public function fastForward(\DateTime $dt) {
+
+        while($this->valid() && $this->getDTEnd() <= $dt) {
+            $this->next();
+        }
+
+    }
+
+    /**
+     * Returns true if this recurring event never ends.
+     *
+     * @return bool
+     */
+    public function isInfinite() {
+
+        return !$this->count && !$this->until;
+
+    }
+
+    /**
+     * Goes on to the next iteration
+     *
+     * @return void
+     */
+    public function next() {
+
+        $previousStamp = $this->currentDate->getTimeStamp();
+
+        // Finding the next overridden event in line, and storing that for
+        // later use.
+        $overriddenEvent = null;
+        $overriddenDate = null;
+        $this->currentOverriddenEvent = null;
+
+        foreach($this->overriddenEvents as $index=>$event) {
+            if ($index > $previousStamp) {
+                $overriddenEvent = $event;
+                $overriddenDate = clone $event->DTSTART->getDateTime();
+                break;
+            }
+        }
+
+        // If we have a stored 'next date', we will use that.
+        if ($this->nextDate) {
+            if (!$overriddenDate || $this->nextDate < $overriddenDate) {
+                $this->currentDate = $this->nextDate;
+                $currentStamp = $this->currentDate->getTimeStamp();
+                $this->nextDate = null;
+            } else {
+                $this->currentDate = clone $overriddenDate;
+                $this->currentOverriddenEvent = $overriddenEvent;
+            }
+            $this->counter++;
+            return;
+        }
+
+        while(true) {
+
+            // Otherwise, we find the next event in the normal RRULE
+            // sequence.
+            switch($this->frequency) {
+
+                case 'hourly' :
+                    $this->nextHourly();
+                    break;
+
+                case 'daily' :
+                    $this->nextDaily();
+                    break;
+
+                case 'weekly' :
+                    $this->nextWeekly();
+                    break;
+
+                case 'monthly' :
+                    $this->nextMonthly();
+                    break;
+
+                case 'yearly' :
+                    $this->nextYearly();
+                    break;
+
+            }
+            $currentStamp = $this->currentDate->getTimeStamp();
+
+
+            // Checking exception dates
+            foreach($this->exceptionDates as $exceptionDate) {
+                if ($this->currentDate == $exceptionDate) {
+                    $this->counter++;
+                    continue 2;
+                }
+            }
+            foreach($this->overriddenDates as $check) {
+                if ($this->currentDate == $check) {
+                    continue 2;
+                }
+            }
+            break;
+
+        }
+
+
+
+        // Is the date we have actually higher than the next overiddenEvent?
+        if ($overriddenDate && $this->currentDate > $overriddenDate) {
+            $this->nextDate = clone $this->currentDate;
+            $this->currentDate = clone $overriddenDate;
+            $this->currentOverriddenEvent = $overriddenEvent;
+            $this->handledOverridden++;
+        }
+        $this->counter++;
+
+
+        /*
+         * If we have overridden events left in the queue, but our counter is
+         * running out, we should grab one of those.
+         */
+        if (!is_null($overriddenEvent) && !is_null($this->count) && count($this->overriddenEvents) - $this->handledOverridden >= ($this->count - $this->counter)) {
+
+            $this->currentOverriddenEvent = $overriddenEvent;
+            $this->currentDate = clone $overriddenDate;
+            $this->handledOverridden++;
+
+        }
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for hourly frequency.
+     *
+     * @return void
+     */
+    protected function nextHourly() {
+
+        if (!$this->byHour) {
+            $this->currentDate->modify('+' . $this->interval . ' hours');
+            return;
+        }
+    }
+
+    /**
+     * Does the processing for advancing the iterator for daily frequency.
+     *
+     * @return void
+     */
+    protected function nextDaily() {
+
+        if (!$this->byHour && !$this->byDay) {
+            $this->currentDate->modify('+' . $this->interval . ' days');
+            return;
+        }
+
+        if (isset($this->byHour)) {
+            $recurrenceHours = $this->getHours();
+        }
+
+        if (isset($this->byDay)) {
+            $recurrenceDays = $this->getDays();
+        }
+
+        do {
+
+            if ($this->byHour) {
+                if ($this->currentDate->format('G') == '23') {
+                    // to obey the interval rule
+                    $this->currentDate->modify('+' . $this->interval-1 . ' days');
+                }
+
+                $this->currentDate->modify('+1 hours');
+
+            } else {
+                $this->currentDate->modify('+' . $this->interval . ' days');
+
+            }
+
+            // Current day of the week
+            $currentDay = $this->currentDate->format('w');
+
+            // Current hour of the day
+            $currentHour = $this->currentDate->format('G');
+
+        } while (($this->byDay && !in_array($currentDay, $recurrenceDays)) || ($this->byHour && !in_array($currentHour, $recurrenceHours)));
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for weekly frequency.
+     *
+     * @return void
+     */
+    protected function nextWeekly() {
+
+        if (!$this->byHour && !$this->byDay) {
+            $this->currentDate->modify('+' . $this->interval . ' weeks');
+            return;
+        }
+
+        if ($this->byHour) {
+            $recurrenceHours = $this->getHours();
+        }
+
+        if ($this->byDay) {
+            $recurrenceDays = $this->getDays();
+        }
+
+        // First day of the week:
+        $firstDay = $this->dayMap[$this->weekStart];
+
+        do {
+
+            if ($this->byHour) {
+                $this->currentDate->modify('+1 hours');
+            } else {
+                $this->currentDate->modify('+1 days');
+            }
+
+            // Current day of the week
+            $currentDay = (int) $this->currentDate->format('w');
+
+            // Current hour of the day
+            $currentHour = (int) $this->currentDate->format('G');
+
+            // We need to roll over to the next week
+            if ($currentDay === $firstDay && (!$this->byHour || $currentHour == '0')) {
+                $this->currentDate->modify('+' . $this->interval-1 . ' weeks');
+
+                // We need to go to the first day of this week, but only if we
+                // are not already on this first day of this week.
+                if($this->currentDate->format('w') != $firstDay) {
+                    $this->currentDate->modify('last ' . $this->dayNames[$this->dayMap[$this->weekStart]]);
+                }
+            }
+
+            // We have a match
+        } while (($this->byDay && !in_array($currentDay, $recurrenceDays)) || ($this->byHour && !in_array($currentHour, $recurrenceHours)));
+    }
+
+    /**
+     * Does the processing for advancing the iterator for monthly frequency.
+     *
+     * @return void
+     */
+    protected function nextMonthly() {
+
+        $currentDayOfMonth = $this->currentDate->format('j');
+        if (!$this->byMonthDay && !$this->byDay) {
+
+            // If the current day is higher than the 28th, rollover can
+            // occur to the next month. We Must skip these invalid
+            // entries.
+            if ($currentDayOfMonth < 29) {
+                $this->currentDate->modify('+' . $this->interval . ' months');
+            } else {
+                $increase = 0;
+                do {
+                    $increase++;
+                    $tempDate = clone $this->currentDate;
+                    $tempDate->modify('+ ' . ($this->interval*$increase) . ' months');
+                } while ($tempDate->format('j') != $currentDayOfMonth);
+                $this->currentDate = $tempDate;
+            }
+            return;
+        }
+
+        while(true) {
+
+            $occurrences = $this->getMonthlyOccurrences();
+
+            foreach($occurrences as $occurrence) {
+
+                // The first occurrence thats higher than the current
+                // day of the month wins.
+                if ($occurrence > $currentDayOfMonth) {
+                    break 2;
+                }
+
+            }
+
+            // If we made it all the way here, it means there were no
+            // valid occurrences, and we need to advance to the next
+            // month.
+            $this->currentDate->modify('first day of this month');
+            $this->currentDate->modify('+ ' . $this->interval . ' months');
+
+            // This goes to 0 because we need to start counting at hte
+            // beginning.
+            $currentDayOfMonth = 0;
+
+        }
+
+        $this->currentDate->setDate($this->currentDate->format('Y'), $this->currentDate->format('n'), $occurrence);
+
+    }
+
+    /**
+     * Does the processing for advancing the iterator for yearly frequency.
+     *
+     * @return void
+     */
+    protected function nextYearly() {
+
+        $currentMonth = $this->currentDate->format('n');
+        $currentYear = $this->currentDate->format('Y');
+        $currentDayOfMonth = $this->currentDate->format('j');
+
+        // No sub-rules, so we just advance by year
+        if (!$this->byMonth) {
+
+            // Unless it was a leap day!
+            if ($currentMonth==2 && $currentDayOfMonth==29) {
+
+                $counter = 0;
+                do {
+                    $counter++;
+                    // Here we increase the year count by the interval, until
+                    // we hit a date that's also in a leap year.
+                    //
+                    // We could just find the next interval that's dividable by
+                    // 4, but that would ignore the rule that there's no leap
+                    // year every year that's dividable by a 100, but not by
+                    // 400. (1800, 1900, 2100). So we just rely on the datetime
+                    // functions instead.
+                    $nextDate = clone $this->currentDate;
+                    $nextDate->modify('+ ' . ($this->interval*$counter) . ' years');
+                } while ($nextDate->format('n')!=2);
+                $this->currentDate = $nextDate;
+
+                return;
+
+            }
+
+            // The easiest form
+            $this->currentDate->modify('+' . $this->interval . ' years');
+            return;
+
+        }
+
+        $currentMonth = $this->currentDate->format('n');
+        $currentYear = $this->currentDate->format('Y');
+        $currentDayOfMonth = $this->currentDate->format('j');
+
+        $advancedToNewMonth = false;
+
+        // If we got a byDay or getMonthDay filter, we must first expand
+        // further.
+        if ($this->byDay || $this->byMonthDay) {
+
+            while(true) {
+
+                $occurrences = $this->getMonthlyOccurrences();
+
+                foreach($occurrences as $occurrence) {
+
+                    // The first occurrence that's higher than the current
+                    // day of the month wins.
+                    // If we advanced to the next month or year, the first
+                    // occurrence is always correct.
+                    if ($occurrence > $currentDayOfMonth || $advancedToNewMonth) {
+                        break 2;
+                    }
+
+                }
+
+                // If we made it here, it means we need to advance to
+                // the next month or year.
+                $currentDayOfMonth = 1;
+                $advancedToNewMonth = true;
+                do {
+
+                    $currentMonth++;
+                    if ($currentMonth>12) {
+                        $currentYear+=$this->interval;
+                        $currentMonth = 1;
+                    }
+                } while (!in_array($currentMonth, $this->byMonth));
+
+                $this->currentDate->setDate($currentYear, $currentMonth, $currentDayOfMonth);
+
+            }
+
+            // If we made it here, it means we got a valid occurrence
+            $this->currentDate->setDate($currentYear, $currentMonth, $occurrence);
+            return;
+
+        } else {
+
+            // These are the 'byMonth' rules, if there are no byDay or
+            // byMonthDay sub-rules.
+            do {
+
+                $currentMonth++;
+                if ($currentMonth>12) {
+                    $currentYear+=$this->interval;
+                    $currentMonth = 1;
+                }
+            } while (!in_array($currentMonth, $this->byMonth));
+            $this->currentDate->setDate($currentYear, $currentMonth, $currentDayOfMonth);
+
+            return;
+
+        }
+
+    }
+
+    /**
+     * Returns all the occurrences for a monthly frequency with a 'byDay' or
+     * 'byMonthDay' expansion for the current month.
+     *
+     * The returned list is an array of integers with the day of month (1-31).
+     *
+     * @return array
+     */
+    protected function getMonthlyOccurrences() {
+
+        $startDate = clone $this->currentDate;
+
+        $byDayResults = array();
+
+        // Our strategy is to simply go through the byDays, advance the date to
+        // that point and add it to the results.
+        if ($this->byDay) foreach($this->byDay as $day) {
+
+            $dayName = $this->dayNames[$this->dayMap[substr($day,-2)]];
+
+            // Dayname will be something like 'wednesday'. Now we need to find
+            // all wednesdays in this month.
+            $dayHits = array();
+
+            $checkDate = clone $startDate;
+            $checkDate->modify('first day of this month');
+            $checkDate->modify($dayName);
+
+            do {
+                $dayHits[] = $checkDate->format('j');
+                $checkDate->modify('next ' . $dayName);
+            } while ($checkDate->format('n') === $startDate->format('n'));
+
+            // So now we have 'all wednesdays' for month. It is however
+            // possible that the user only really wanted the 1st, 2nd or last
+            // wednesday.
+            if (strlen($day)>2) {
+                $offset = (int)substr($day,0,-2);
+
+                if ($offset>0) {
+                    // It is possible that the day does not exist, such as a
+                    // 5th or 6th wednesday of the month.
+                    if (isset($dayHits[$offset-1])) {
+                        $byDayResults[] = $dayHits[$offset-1];
+                    }
+                } else {
+
+                    // if it was negative we count from the end of the array
+                    $byDayResults[] = $dayHits[count($dayHits) + $offset];
+                }
+            } else {
+                // There was no counter (first, second, last wednesdays), so we
+                // just need to add the all to the list).
+                $byDayResults = array_merge($byDayResults, $dayHits);
+
+            }
+
+        }
+
+        $byMonthDayResults = array();
+        if ($this->byMonthDay) foreach($this->byMonthDay as $monthDay) {
+
+            // Removing values that are out of range for this month
+            if ($monthDay > $startDate->format('t') ||
+                $monthDay < 0-$startDate->format('t')) {
+                    continue;
+            }
+            if ($monthDay>0) {
+                $byMonthDayResults[] = $monthDay;
+            } else {
+                // Negative values
+                $byMonthDayResults[] = $startDate->format('t') + 1 + $monthDay;
+            }
+        }
+
+        // If there was just byDay or just byMonthDay, they just specify our
+        // (almost) final list. If both were provided, then byDay limits the
+        // list.
+        if ($this->byMonthDay && $this->byDay) {
+            $result = array_intersect($byMonthDayResults, $byDayResults);
+        } elseif ($this->byMonthDay) {
+            $result = $byMonthDayResults;
+        } else {
+            $result = $byDayResults;
+        }
+        $result = array_unique($result);
+        sort($result, SORT_NUMERIC);
+
+        // The last thing that needs checking is the BYSETPOS. If it's set, it
+        // means only certain items in the set survive the filter.
+        if (!$this->bySetPos) {
+            return $result;
+        }
+
+        $filteredResult = array();
+        foreach($this->bySetPos as $setPos) {
+
+            if ($setPos<0) {
+                $setPos = count($result)-($setPos+1);
+            }
+            if (isset($result[$setPos-1])) {
+                $filteredResult[] = $result[$setPos-1];
+            }
+        }
+
+        sort($filteredResult, SORT_NUMERIC);
+        return $filteredResult;
+
+    }
+
+    protected function getHours()
+    {
+        $recurrenceHours = array();
+        foreach($this->byHour as $byHour) {
+            $recurrenceHours[] = $byHour;
+        }
+
+        return $recurrenceHours;
+    }
+
+    protected function getDays()
+    {
+        $recurrenceDays = array();
+        foreach($this->byDay as $byDay) {
+
+            // The day may be preceeded with a positive (+n) or
+            // negative (-n) integer. However, this does not make
+            // sense in 'weekly' so we ignore it here.
+            $recurrenceDays[] = $this->dayMap[substr($byDay,-2)];
+
+        }
+
+        return $recurrenceDays;
+    }
+}
+