Yii Framework 2.0 Rules Date Validator

Question

I am using Yii Framework 2.0. I have a form with a text input field which is meant for a date. I have read the Yii Framework 2.0 about the Class yii\validators\Validator and known all the validator keys which can be used inside of the rules() method in a model class. When I use the date key as below, it does not validate anything. It means that I still can put some text in that input field and can post the form.

When I changed it into boolean or email, I could see that it validates very well when I put something wrong in the input field. How can I validate a date value inside of an input field with Yii Framework 2.0?

My rules() method:

public function rules()
{
    return [
         [['inputfield_date'], 'required'],
         [['inputfield_date'], 'safe'],
         [['inputfield_date'], 'date'],
    ];
}

My view page:

<?php $form = ActiveForm::begin(); ?>
     <?= $form->field($model, 'inputfield_date')->textInput(); ?>
<?php ActiveForm::end(); ?>

Answer 1

Boy the Yii docs suck. They don't even give an example. Working from O'Connor's answer, this worked for me since I was assigning the value in 2015-09-11 format.

// Rule
[['event_date'], 'date', 'format' => 'php:Y-m-d']
// Assignment
$agkn->event_date = date('Y-m-d');

The docs don't even specify where format or timestampAttribute came from, or how to use them. It doesn't even say what the heck from_date and to_date are. And most of all, no examples!