Date & Time fields don't have labels for their individual elements

Patch to add invisible labels, so screen readers can read the label.

New version that doesn't add a label for the time period because the individual radio button elements have their own labels.

The purpose here is to set titles for screen readers so setting them to null would not help.

$none is the visible value of the empty/none option for each of the date parts, which is either t('Day'), t('Month'), or t('Year').

This is the code in question:

<?php
  // Set defaults according to existing #default_value (set by Form API)
  if (isset($element['#default_value']['month']) || isset($element['#default_value']['day']) || isset($element['#default_value']['year'])) {
    $default_values = array(
      'month' => $element['#default_value']['month'],
      'day' => $element['#default_value']['day'],
      'year' => $element['#default_value']['year'],
    );
  }
  else {
    $default_values = array(
      'day' => NULL,
      'month' => NULL,
      'year' => NULL,
    );
  }

  // Let Drupal do it's normal expansion.
  $element = form_process_date($element);

  // Set default values.
  foreach ($default_values as $type => $value) {
    switch ($type) {
      case 'month':
        $none = t('Month');
        break;
      case 'day':
        $none = t('Day');
        break;
      case 'year':
        $none = t('Year');
        break;
    }
    unset($element[$type]['#value']);
    $element[$type]['#default_value'] = isset($default_values[$type]) ? $default_values[$type] : NULL;
    $element[$type]['#options'] = array('' => $none) + $element[$type]['#options'];
  }
?>