using hook_element_info() to add a placeholder to a form label

Hi.

I am trying to add a placeholder to the date field by using hook_element_info_alter(). There are really few examples of how to do this to add a placeholder, but for some reason it is not working. This is what I am doing:

/**
 * Implementation of hook_element_info_alter().
 */
function customize_register_form_element_info_alter(&$type) {
  if (isset($type['text'])) {
    $type['text']['#process'][] = 'customize_register_form_text';
  }
}

/**
 * Function for editing label.
 */
function customize_register_form_process_text($element) {
  if ($_GET['q'] == 'user/register') {
    if ($element['#array_parents'][0] == 'account') {
      $element['user_user_form_group_user_birth']['#attributes']['placeholder'] = t('00/00/0000');
    }
  }
  return $element;
}


Could you please help me?

Thanks in advance,

Winter