public function format_datetime($field)
    {
        $d = $this->current_row[$field];
        if (!$d) {
            $this->current_row[$field] = '-';
        } else {
            if ($d instanceof MongoDate) {
                $this->current_row[$field] = date(
                    $this->app->getConfig('locale/datetime', 'd/m/Y H:i:s'),
                    $d->sec
                );
            } elseif (is_numeric($d)) {
                $this->current_row[$field] = date(
                    $this->app->getConfig('locale/datetime', 'd/m/Y H:i:s'),
                    $d
                );
            } elseif ($d instanceof \DateTime) {
                $this->current_row[$field] = $d->format($this->app->getConfig('locale/datetime', 'd/m/Y H:i:s'));
            } else {
                $d = strtotime($d);
                $this->current_row[$field] = $d
                    ? date(
                        $this->app->getConfig('locale/datetime', 'd/m/Y H:i:s'),
                        $d
                    )
                    : '-';
            }
        }
    }