Adminhtml form date input type default format wrong

Question

I've managed to create an Adminhtml form extending \Magento\Backend\Block\Widget\Form\Generic.
I've added each field inside _prepareForm() method using $fieldset->addField() method.
One of the fields is

  $fieldset->addField(
             'birthdate',
             'date',
             [
                 'name' => 'birthdate',
                 'label' => __('Birthdate'),
                 'title' => __('Birthdate'),
                 'required' => true,
                 'class' => '',
                 'singleClick'=> true,
                 'format'=>'dd-MM-yyyy',
                 'time'=>false
                //'format' =>$this->_localeDate->getDateFormat(\IntlDateFormatter::LONG)
             ]
         );

Now... neither formats is taken into account when the form is populated (editing a record). The default value that is read from DB is 1995-12-12.
but the form displays Tuesday, December 12, 1995 at 12:00:00 AM Eastern European Standard Time. When I'm setting the date from the calendar, the format is the desired one.

How can I specify the form to load the data with proper format?

Answer 1

For correct date's output use date_format property

  $fieldset->addField(
         'birthdate',
         'date',
         [
             'name' => 'birthdate',
             'label' => __('Birthdate'),
             'title' => __('Birthdate'),
             'required' => true,
             'class' => '',
             'singleClick'=> true,
             'date_format' => 'yyyy-MM-dd', **//Like this one**
             'time'=>false
            //'format' =>$this->_localeDate->getDateFormat(\IntlDateFormatter::LONG)
         ]
     );

Answer 2

You can use: beforeSave() in your Model to convert the input.

for Example: inject Magento\Framework\Stdlib\DateTime as $this->_date than:

1. convert Timestamp<br> $timestamp = $this->_date->timestamp($this->getDate();
   
2. convert gmtDate<br> $birthdate = $this->_date->gmtDate('y-m-d',$timestamp);
   
3. $birthdate to object<br> $this->setBirthdate($birthdate);

$this->setBirthdate($this->_date->gmtDate('y-m-d',$this->_date->timestamp($this->getDate())));

//*dirty workaround.