Form/Type/DatepickerType.php
public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        parent::setDefaultOptions($resolver);
        
        $resolver->setDefaults(array(
            'widget'         => 'single_text',
            'widget_options'  => array(
              'showButtonPanel' => true,
              'changeMonth'=> true, 
              'changeYear'=>  true
            ),
        ));
        
        $resolver->setAllowedValues(array(
            'input'     => array(
                'datetime',
                'string',
                'timestamp',
                'array',
            ),
            'widget'    => array(
                'single_text',
            ),
        ));
        
    }
public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        parent::setDefaultOptions($resolver);
        
        $resolver->setDefaults(array(
            'widget'         => 'single_text',
            'widget_options'  => array(
              'showButtonPanel' => true,
              'changeMonth'=> true, 
              'changeYear'=>  true
            ),
        ));
        
        $resolver->setAllowedValues(array(
            'input'     => array(
                'datetime',
                'string',
                'timestamp',
                'array',
            ),
            'widget'    => array(
                'single_text',
            ),
        ));
        
    }
{@inheritdoc}