/**
  * Converts dateTime from local TZ to UTC
  * Returns dateTime in format expected by the Outlook API
  * 
  * @param  dateTime $dateTime
  * @return dateTime
  */
 protected static function encodeDateTime($dateTime)
 {
     $utcDateTime = $dateTime->setTimeZone(new \DateTimeZone("UTC"));
     $dateFormat = "Y-m-d\\TH:i:s\\Z";
     return date_format($utcDateTime, $dateFormat);
 }