public function actionCreate($col = null)
 {
     $model = new Calendar();
     if ($col !== null) {
         $model->collection_id = $col;
     }
     if ($model->load(\yii::$app->request->post()) && $model->save()) {
         Yii::$app->session->setFlash('success', sprintf('Calendar %s has been created', $model->title));
         return $this->redirect(['/collections/default/manage', 'id' => $model->collection_id]);
     } else {
         return $this->render('create', ['model' => $model]);
     }
 }