Change labels of date select fields

Question

I'm using the Form API to create a Date of Birth field with lists for month, day and year.

$form['dob'] = array(
    '#type' => 'date_select',
    '#title' => t('Date of birth'),
    '#default_value' => '',
    '#date_format' => 'm-d-Y',
    '#date_label_position' => 'within',
    '#date_year_range' => '-100:+0',
    '#required' => TRUE,
);

Sine the default value is blank this outputs the following:

How can I alter the labels? Specifically I want to get rid of the '-' characters so it looks more like this

Answer 1

There might be better way to do this, but one method would be to run an #after_build function that will alter the first '' placeholder date label option to your liking. For example:

/**
 * Implements hook_form_alter().
 */
function MYMODULE_form_alter(&$form, &$form_state, $form_id) {     
  $form['dob'] = array(
    '#type' => 'date_select',
    '#title' => t('Date of birth'),
    '#default_value' => '',
    '#date_format' => 'm-d-Y',
    '#date_label_position' => 'within',
    '#date_year_range' => '-100:+0',
    '#required' => TRUE,
  );
  $form['dob']['#after_build'][] = 'MYMODULE_myform_dob_after_build';
}

// Alter the date component option so the first placeholder element has the new label.
function MYMODULE_myform_dob_after_build(&$form, &$form_state) {
  $form['day']['#options'][''] = t('Day');
  $form['month']['#options'][''] = t('Month');
  $form['year']['#options'][''] = t('Year');
  return $form;
}