Set default value on Datetime field in symfony2 form

I have a form containing several fields. One of them is a Datetime field. How to define a default value for that field?

I've tried setting a value on the related entity, in controller, in constructor and __construct :

$myEntity = new MyEntity();
$myEntity->setMyDate(new \DateTime());
$form = $this->createForm(new AddMyEntity(), $myEntity);

Not working.

Tried to define the $data variable in the buildForm :

$builder->add('myDate', 'date', array(
    'format' => \IntlDateFormatter::SHORT,
    'input' => 'datetime',
    'widget' => 'single_text',
    'data' => new \DateTime("now"));

Not working either. Any ideas, Symfony2 community?

EDIT : Adding entity on demand of faost.

/**
 * @ORM\Column(name="myDate", type="datetime")
 * @Assert\NotBlank()
 */
private $myDate;

Solution 1:

Set it in the entity constructor:

class Entity
{
    /**
     * @var \DateTime
     */
    private $date;

    public function __construct()
    {
        $this->date = new \DateTime();
    }
}

Solution 2:

Elnur's answer is correct and is perhaps the recommended one. But for completeness, an alternative way to set the default value for a date widget in a form is to specify the data key in the options array argument with an instance of DateTime.

$builder->add('myDate', 'date', array(
    'data' => new \DateTime()
));

Note: This will overwrite the previously set datetime on every edit.