如何解决错误的请求（＃400）无法验证您在yii2中提交的数据？

在提交表单时出现此错误：

I have got this error, when submit the form:

Bad Request (#400) Unable to verify your data submission.

我有<？= Html :: csrfMetaTags（）？> 。我认为，我有这个问题，因为我使用了datepicker。使用ActiveForm创建表单。

I have got <?= Html::csrfMetaTags() ?> in the layout. I think, that this problems I have, because I use datepicker. Form create with ActiveForm.

我必须做什么？这里是表格的代码：

What I must to do? Here is code of the form:

<?
        $form2 = ActiveForm::begin(['id' => 'user-univer']);
        echo $form2->field($model2, 'university')->label('Input university name:');
        echo $form2->field($model2, 'degree')->label('Input your education specialization:');
        //echo $form2->field($model2, 'date')->label('Input your education date:');
        echo '<label class="control-label">Education time:</label><br/>';
        echo '<span>Start date of your education:</span>';
        echo DatePicker::widget([
            'name'  => 'date_from',
            'value'  => $value,
            'dateFormat' => 'dd.MM.yyyy',
        ]);
        echo '<span>End date of your education:</span>';
        echo DatePicker::widget([
            'name'  => 'date_to',
            'value'  => $value,
            'dateFormat' => 'dd.MM.yyyy',    
        ]);
        echo '<br/><br/>';


        echo $form2->field($model2, 'info')->textarea()->label('Any other information about your university degree:');
        echo Html::submitButton('Add university', ['class' => 'btn btn-primary btn-univer']);
        ActiveForm::end(['id' => 'user-univer']);

        } ?>

UPD：没有datepicker我有同样的问题，为什么？如何解决它？

UPD: without datepicker I have got the same problems, why? how to solve it?