private function format_i(&$str) {
    if (strstr($str, '%i'))
      $str = str_replace('%i', sprintf('%02d', $this->min), $str);
  }
private function format_i(&$str) {
    if (strstr($str, '%i'))
      $str = str_replace('%i', sprintf('%02d', $this->min), $str);
  }
Minutes with leading zeros
@param type $str