private function formatD(&$str) {
    if (strstr($str, '%D'))
      $str = str_replace('%D', $this->dayName(false), $str);
  }
private function formatD(&$str) {
    if (strstr($str, '%D'))
      $str = str_replace('%D', $this->dayName(false), $str);
  }
Textual representation of a day, three letters
@param string $str