Coming from #507502-33: (needs documentation) Provide Locale support for jQuery UI, instead of patching core, I did this:

<?php
/**
* Implementation of hook_library_alter()
*
* Support localized date picker. See drupal.org/node/507502#comment-4534106.
*/
function my_module_library_alter(&$libraries, $module) {
  global
$language;
  if (
$module == 'system' && isset($libraries['ui.datepicker'])) {
   
$datepicker = drupal_get_path('module', 'locale') . '/locale.datepicker.js';
   
$libraries['ui.datepicker']['js'][$datepicker] = array('scope' => 'footer', 'group' => JS_THEME);
   
$libraries['ui.datepicker']['js'][] = array(
     
'data' => array(
       
'jqueryuidatepicker' => array(
         
'rtl' => $language->direction == LANGUAGE_RTL,
         
'firstDay' => variable_get('date_first_day', 0),
        ),
      ),
     
'type' => 'setting',
    );
  }
}
?>

This could probably be tweaked to less intrusive, but until that D7 patch lands, I thought maybe others could use this option.