function createCalscale() {
    if( !isset( $this->calscale ))
      return;
    switch( $this->format ) {
      case 'xcal':
        return ' calscale="'.$this->calscale.'"'.$this->nl;
        break;
      default:
        return 'CALSCALE:'.$this->calscale.$this->nl;
        break;
    }
  }