/**
  * Convert any value to date time.
  *
  * @param $value
  *
  * @return \DateTime|null
  */
 protected function convertToDateTime($value)
 {
     if ($value instanceof \DateTime) {
         return clone $value;
     }
     if ($value instanceof \MongoDate) {
         $datetime = new \DateTime();
         $datetime->setTimestamp($value->sec);
         return $datetime;
     }
     if (is_numeric($value)) {
         $datetime = new \DateTime();
         $datetime->setTimestamp($value);
         return $datetime;
     }
     if (is_string($value) && !empty($value)) {
         $datetime = new \DateTime($value);
         return $datetime;
     }
     return;
 }