public function __construct()
{
$this->date0 = isset(Yii::$app->request->queryParams['BooksSearch']['date0']) ? Yii::$app->request->queryParams['BooksSearch']['date0'] : '';
$this->date1 = isset(Yii::$app->request->queryParams['BooksSearch']['date1']) ? Yii::$app->request->queryParams['BooksSearch']['date1'] : '';
parent::__construct();
}