/**
  * Formats cell's content.
  * @param  mixed
  * @param  DibiRow|array
  * @return string
  */
 public function formatContent($value, $data = NULL)
 {
     if ((int) $value == NULL || empty($value)) {
         return 'N/A';
     }
     $value = parent::formatContent($value, $data);
     $value = is_numeric($value) ? (int) $value : ($value instanceof DateTime ? $value->format('U') : strtotime($value));
     return strftime($this->format, $value);
 }