如何让Symfony FormComponent以非常特殊的格式初始化DateTime？

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\DateTimeType;
use Symfony\Component\Form\FormBuilderInterface;

class MyFormType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('myDateTime', DateTimeType::class, [
                'widget' => 'single_text',
                'input' => 'string',
                'format' => 'Y-m-d H:i:s',
                'html5' => false,
                'attr' => [
                    'class' => 'special-datetime-picker',
                ],
            ]);
    }
}

use Symfony\Component\Form\FormFactoryInterface;
use Symfony\Component\HttpFoundation\Request;

class MyController
{
    private $formFactory;

    public function __construct(FormFactoryInterface $formFactory)
    {
        $this->formFactory = $formFactory;
    }

    public function myAction(Request $request)
    {
        $form = $this->formFactory->create(MyFormType::class);

        // 处理表单提交
        $form->handleRequest($request);
        if ($form->isSubmitted() && $form->isValid()) {
            // 处理表单数据
            $data = $form->getData();
            // ...
        }

        return $this->render('my_template.html.twig', [
            'form' => $form->createView(),
        ]);
    }
}