Cannot set unbound field constraint in Symfony - forms

Question

I'm trying to do as easy thing as make the date field not to be set under "now" value. I'd emphasise that this date field is not linked to any Entity. Symfony keeps ignoring constraint even though I set it in two places:
1. Constraint set in the class definition
This is the first thing I've done. I decided to put this constraint directly where I define this date field
namespace Asmox\BubblechecklistBundle\Form\Type;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Validator\Constraints\LessThanOrEqual;
class DeadlineType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options) {
$builder->add('date', 'datetime',array(
'mapped' => false,
'date_format' => 'dd MMMM yyyy',
'constraints' => array(
new LessThanOrEqual("now")
)
));
}
2. Constraint set in the validation.yml file
I also added constraint into separate file, because the first way didn't give the results:
Asmox\BubblechecklistBundle\Form\Type\DeadlineType:
properties:
date:
- LessThanOrEqual: now
I ensured that I have enabled validation in both my configuration files (for prod and dev):
validation: { enabled: true, enable_annotations: true }
But every time I try to submit form with date earlier than now, Symfony pass it. I don't know what I can do more. Please take a look on my paste from Controller:
public function newTaskAction(Request $request)
{
// ...
$form = $this->createForm(new TaskType());
if ($request->getMethod() == 'POST') {
$form->bind($request);
if ($form->isValid()) {
// Add new task...
// Redirect to the task list
$this->addFlash('notice', 'I've added new task!');
return $this->redirectToRoute('tasksList');
}
else {
// Create view with form if form is not validate
$request = $this->getRequest();
$request->setLocale('pl');
if ($mobileDetector->isMobile())
$template = 'AsmoxBubblechecklistBundle:Task:taskFormPhone.html.twig';
else
$template = 'AsmoxBubblechecklistBundle:Task:taskForm.html.twig';
return $this->render($template, array('form'=>$form->createView()));
}
}
else {
// Create view with form if request isn't POST
$request = $this->getRequest();
$request->setLocale('pl');
// Utwórz widok
if ($mobileDetector->isMobile())
$template = 'AsmoxBubblechecklistBundle:Task:taskFormPhone.html.twig';
else
$template = 'AsmoxBubblechecklistBundle:Task:taskForm.html.twig';
return $this->render($template, array('form'=>$form->createView()));
}
}
Whats wrong?