protected function processDates() {
        if (is_array($this->data)) {
            foreach ($this->data as &$row) {
                if ($row[0] instanceof \DateTimeInterface)
                    $row[0] = new JsExpression("new Date(".($row[0]->getTimestamp()*1000).")");
                elseif ($this->xIsDate)
                    $row[0] = new JsExpression("new Date('$row[0]')");
            }
            return Json::encode($this->data, JSON_NUMERIC_CHECK);
        }
        return Json::encode($this->data);
    }