ICal\ICal::iCalDateToUnixTimestamp PHP Method

    public function iCalDateToUnixTimestamp($icalDate)
    {
        /**
         * iCal times may be in 3 formats, ref http://www.kanzaki.com/docs/ical/dateTime.html
         * UTC:      Has a trailing 'Z'
         * Floating: No timezone reference specified, no trailing 'Z', use local time
         * TZID:     Set timezone as specified
         * Use DateTime class objects to get around limitations with mktime and gmmktime. Must have a local timezone set
         * to process floating times.
         */
        $pattern = '/\\AT?Z?I?D?=?(.*):?';
        // 1: TimeZone
        $pattern .= '([0-9]{4})';
        // 2: YYYY
        $pattern .= '([0-9]{2})';
        // 3: MM
        $pattern .= '([0-9]{2})';
        // 4: DD
        $pattern .= 'T?';
        //    Time delimiter
        $pattern .= '([0-9]{0,2})';
        // 5: HH
        $pattern .= '([0-9]{0,2})';
        // 6: MM
        $pattern .= '([0-9]{0,2})';
        // 7: SS
        $pattern .= '(Z?)/';
        // 8: UTC flag
        preg_match($pattern, $icalDate, $date);
        $timezone = str_replace(':', '', $date[1]);
        // Unix timestamp can't represent dates before 1970
        if ($date[2] <= self::UNIX_MIN_YEAR) {
            return false;
        }
        // Unix timestamps after 03:14:07 UTC 2038-01-19 might cause an overflow
        // if 32 bit integers are used.
        if ($date[8] == 'Z') {
            $convDate = new \DateTime('now', new \DateTimeZone('UTC'));
        } else {
            if (!$timezone) {
                $convDate = new \DateTime('now', new \DateTimeZone($this->calendarTimeZone()));
            } else {
                if ($this->isValidTimeZoneId($timezone)) {
                    $convDate = new \DateTime('now', new \DateTimeZone($timezone));
                } else {
                    $convDate = new \DateTime('now', new \DateTimeZone(date_default_timezone_get()));
                }
            }
        }
        $convDate->setDate((int) $date[2], (int) $date[3], (int) $date[4]);
        $convDate->setTime((int) $date[5], (int) $date[6], (int) $date[7]);
        $timestamp = $convDate->getTimestamp();
        return $timestamp;
    }

 /**
  * Imports ical files.
  *
  * @param UploadedFile $file
  * @param Workspace    $workspace
  *
  * @return int number of events saved
  */
 public function importEvents(UploadedFile $file, $workspace = null)
 {
     $ical = new ICal($file->getPathname());
     $events = $ical->events();
     $tabs = [];
     foreach ($events as $event) {
         $e = new Event();
         $e->setTitle($event->summary);
         $e->setStart($ical->iCalDateToUnixTimestamp($event->dtstart));
         $e->setEnd($ical->iCalDateToUnixTimestamp($event->dtend));
         $e->setDescription($event->description);
         if ($workspace) {
             $e->setWorkspace($workspace);
         }
         $e->setUser($this->tokenStorage->getToken()->getUser());
         $e->setPriority('#01A9DB');
         $this->om->persist($e);
         //the flush is required to generate an id
         $this->om->flush();
         $tabs[] = $e->jsonSerialize();
     }
     return $tabs;
 }