--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/libcalendaring/lib/Sabre/VObject/Property/DateTime.php	Sat Jan 13 08:57:56 2018 -0500
@@ -0,0 +1,245 @@
+<?php
+
+namespace Sabre\VObject\Property;
+
+use Sabre\VObject;
+
+/**
+ * DateTime property
+ *
+ * This element is used for iCalendar properties such as the DTSTART property.
+ * It basically provides a few helper functions that make it easier to deal
+ * with these. It supports both DATE-TIME and DATE values.
+ *
+ * In order to use this correctly, you must call setDateTime and getDateTime to
+ * retrieve and modify dates respectively.
+ *
+ * If you use the 'value' or properties directly, this object does not keep
+ * reference and results might appear incorrectly.
+ *
+ * @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 DateTime extends VObject\Property {
+
+    /**
+     * Local 'floating' time
+     */
+    const LOCAL = 1;
+
+    /**
+     * UTC-based time
+     */
+    const UTC = 2;
+
+    /**
+     * Local time plus timezone
+     */
+    const LOCALTZ = 3;
+
+    /**
+     * Only a date, time is ignored
+     */
+    const DATE = 4;
+
+    /**
+     * DateTime representation
+     *
+     * @var \DateTime
+     */
+    protected $dateTime;
+
+    /**
+     * dateType
+     *
+     * @var int
+     */
+    protected $dateType;
+
+    /**
+     * Updates the Date and Time.
+     *
+     * @param \DateTime $dt
+     * @param int $dateType
+     * @return void
+     */
+    public function setDateTime(\DateTime $dt, $dateType = self::LOCALTZ) {
+
+        switch($dateType) {
+
+            case self::LOCAL :
+                $this->setValue($dt->format('Ymd\\THis'));
+                $this->offsetUnset('VALUE');
+                $this->offsetUnset('TZID');
+                $this->offsetSet('VALUE','DATE-TIME');
+                break;
+            case self::UTC :
+                $dt->setTimeZone(new \DateTimeZone('UTC'));
+                $this->setValue($dt->format('Ymd\\THis\\Z'));
+                $this->offsetUnset('VALUE');
+                $this->offsetUnset('TZID');
+                $this->offsetSet('VALUE','DATE-TIME');
+                break;
+            case self::LOCALTZ :
+                $this->setValue($dt->format('Ymd\\THis'));
+                $this->offsetUnset('VALUE');
+                $this->offsetUnset('TZID');
+                $this->offsetSet('VALUE','DATE-TIME');
+                $this->offsetSet('TZID', $dt->getTimeZone()->getName());
+                break;
+            case self::DATE :
+                $this->setValue($dt->format('Ymd'));
+                $this->offsetUnset('VALUE');
+                $this->offsetUnset('TZID');
+                $this->offsetSet('VALUE','DATE');
+                break;
+            default :
+                throw new \InvalidArgumentException('You must pass a valid dateType constant');
+
+        }
+        $this->dateTime = $dt;
+        $this->dateType = $dateType;
+
+    }
+
+    /**
+     * Returns the current DateTime value.
+     *
+     * If no value was set, this method returns null.
+     *
+     * @return \DateTime|null
+     */
+    public function getDateTime() {
+
+        if ($this->dateTime)
+            return $this->dateTime;
+
+        list(
+            $this->dateType,
+            $this->dateTime
+        ) = self::parseData($this->value, $this);
+        return $this->dateTime;
+
+    }
+
+    /**
+     * Returns the type of Date format.
+     *
+     * This method returns one of the format constants. If no date was set,
+     * this method will return null.
+     *
+     * @return int|null
+     */
+    public function getDateType() {
+
+        if ($this->dateType)
+            return $this->dateType;
+
+        list(
+            $this->dateType,
+            $this->dateTime,
+        ) = self::parseData($this->value, $this);
+        return $this->dateType;
+
+    }
+
+    /**
+     * This method will return true, if the property had a date and a time, as
+     * opposed to only a date.
+     *
+     * @return bool
+     */
+    public function hasTime() {
+
+        return $this->getDateType()!==self::DATE;
+
+    }
+
+    /**
+     * Parses the internal data structure to figure out what the current date
+     * and time is.
+     *
+     * The returned array contains two elements:
+     *   1. A 'DateType' constant (as defined on this class), or null.
+     *   2. A DateTime object (or null)
+     *
+     * @param string|null $propertyValue The string to parse (yymmdd or
+     *                                   ymmddThhmmss, etc..)
+     * @param \Sabre\VObject\Property|null $property The instance of the
+     *                                              property we're parsing.
+     * @return array
+     */
+    static public function parseData($propertyValue, VObject\Property $property = null) {
+
+        if (is_null($propertyValue)) {
+            return array(null, null);
+        }
+
+        $date = '(?P<year>[1-2][0-9]{3})(?P<month>[0-1][0-9])(?P<date>[0-3][0-9])';
+        $time = '(?P<hour>[0-2][0-9])(?P<minute>[0-5][0-9])(?P<second>[0-5][0-9])';
+        $regex = "/^$date(T$time(?P<isutc>Z)?)?$/";
+
+        if (!preg_match($regex, $propertyValue, $matches)) {
+            throw new \InvalidArgumentException($propertyValue . ' is not a valid \DateTime or Date string');
+        }
+
+        if (!isset($matches['hour'])) {
+            // Date-only
+            return array(
+                self::DATE,
+                new \DateTime($matches['year'] . '-' . $matches['month'] . '-' . $matches['date'] . ' 00:00:00', new \DateTimeZone('UTC')),
+            );
+        }
+
+        $dateStr =
+            $matches['year'] .'-' .
+            $matches['month'] . '-' .
+            $matches['date'] . ' ' .
+            $matches['hour'] . ':' .
+            $matches['minute'] . ':' .
+            $matches['second'];
+
+        if (isset($matches['isutc'])) {
+            $dt = new \DateTime($dateStr,new \DateTimeZone('UTC'));
+            $dt->setTimeZone(new \DateTimeZone('UTC'));
+            return array(
+                self::UTC,
+                $dt
+            );
+        }
+
+        // Finding the timezone.
+        $tzid = $property['TZID'];
+        if (!$tzid) {
+            // This was a floating time string. This implies we use the
+            // timezone from date_default_timezone_set / date.timezone ini
+            // setting.
+            return array(
+                self::LOCAL,
+                new \DateTime($dateStr)
+            );
+        }
+
+        // To look up the timezone, we must first find the VCALENDAR component.
+        $root = $property;
+        while($root->parent) {
+            $root = $root->parent;
+        }
+        if ($root->name === 'VCALENDAR') {
+            $tz = VObject\TimeZoneUtil::getTimeZone((string)$tzid, $root);
+        } else {
+            $tz = VObject\TimeZoneUtil::getTimeZone((string)$tzid);
+        }
+
+        $dt = new \DateTime($dateStr, $tz);
+        $dt->setTimeZone($tz);
+
+        return array(
+            self::LOCALTZ,
+            $dt
+        );
+
+    }
+
+}