Symfony\Component\Form\Extension\Core\Type\DateTimeType::buildForm PHP Method

    public function buildForm(FormBuilder $builder, array $options)
    {
        $parts = array('year', 'month', 'day', 'hour', 'minute');
        $timeParts = array('hour', 'minute');

        $format = 'Y-m-d H:i:00';
        if ($options['with_seconds']) {
            $format = 'Y-m-d H:i:s';

            $parts[] = 'second';
            $timeParts[] = 'second';
        }

        if ($options['date_widget'] !== $options['time_widget']) {
            throw new FormException(sprintf('Options "date_widget" and "time_widget" need to be identical. Used: "date_widget" = "%s" and "time_widget" = "%s".', $options['date_widget'] ?: 'choice', $options['time_widget'] ?: 'choice'));
        }

        if ($options['widget'] === 'single_text') {
            $builder->appendClientTransformer(new DateTimeToStringTransformer($options['data_timezone'], $options['user_timezone'], $format));
        } else {
            // Only pass a subset of the options to children
            $dateOptions = array_intersect_key($options, array_flip(array(
                'years',
                'months',
                'days',
                'empty_value',
                'required',
            )));
            $timeOptions = array_intersect_key($options, array_flip(array(
                'hours',
                'minutes',
                'seconds',
                'with_seconds',
                'empty_value',
                'required',
            )));

            // If `widget` is set, overwrite widget options from `date` and `time`
            if (isset($options['widget'])) {
                $dateOptions['widget'] = $options['widget'];
                $timeOptions['widget'] = $options['widget'];
            } else {
                if (isset($options['date_widget'])) {
                    $dateOptions['widget'] = $options['date_widget'];
                }

                if (isset($options['time_widget'])) {
                    $timeOptions['widget'] = $options['time_widget'];
                }
            }

            if (isset($options['date_format'])) {
                $dateOptions['format'] = $options['date_format'];
            }

            $dateOptions['input'] = 'array';
            $timeOptions['input'] = 'array';

            $builder
                ->appendClientTransformer(new DataTransformerChain(array(
                    new DateTimeToArrayTransformer($options['data_timezone'], $options['user_timezone'], $parts),
                    new ArrayToPartsTransformer(array(
                        'date' => array('year', 'month', 'day'),
                        'time' => $timeParts,
                    )),
                )))
                ->add('date', 'date', $dateOptions)
                ->add('time', 'time', $timeOptions)
            ;
        }

        if ($options['input'] === 'string') {
            $builder->appendNormTransformer(new ReversedTransformer(
                new DateTimeToStringTransformer($options['data_timezone'], $options['data_timezone'], $format)
            ));
        } else if ($options['input'] === 'timestamp') {
            $builder->appendNormTransformer(new ReversedTransformer(
                new DateTimeToTimestampTransformer($options['data_timezone'], $options['data_timezone'])
            ));
        } else if ($options['input'] === 'array') {
            $builder->appendNormTransformer(new ReversedTransformer(
                new DateTimeToArrayTransformer($options['data_timezone'], $options['data_timezone'], $parts)
            ));
        }

        $builder->setAttribute('widget', $options['widget']);
    }

 public function buildForm(FormBuilderInterface $builder, array $options)
 {
     parent::buildForm($builder, $options);
     $dateFieldOptions = $builder->get('date')->getOptions();
     $dateFieldOptions['attr'] = array('placeholder' => 'día/mes/año', 'class' => 'tapir-input-120 tapir-input-fecha');
     $builder->remove('date');
     $builder->add('date', 'Symfony\\Component\\Form\\Extension\\Core\\Type\\DateType', $dateFieldOptions);
     $timeFieldOptions = $builder->get('time')->getOptions();
     $timeFieldOptions['label'] = '-';
     $timeFieldOptions['attr'] = array('placeholder' => 'h:m', 'class' => 'tapir-input-80 tapir-input-hora');
     $builder->remove('time');
     $builder->add('time', 'Symfony\\Component\\Form\\Extension\\Core\\Type\\TimeType', $timeFieldOptions);
     //echo '<pre>'; print_r($builder->get('time')->getOptions());
 }