Archive widget numbers translation?

For archives you can use the get_archives_link filter like this:

add_filter('get_archives_link', 'translate_archive_month');
function translate_archive_month($list) {

  $patterns = array( 
    '/January/', '/February/', '/March/', '/April/', '/May/', '/June/',
    '/July/', '/August/', '/September/', '/October/',  '/November/', '/December/'
  );

  $replacements = array( //Put here whatever you want
    '01', '02', '03', '04', '05', '06', 
    '07', '08', '09', '10', '11', '12'
  );    

  $list = preg_replace($patterns, $replacements, $list);
return $list; 
}

Hope it helps.