code: public void setWeekOfYearVisible(boolean weekOfYearVisible) {
  		if (weekOfYearVisible == this.weekOfYearVisible) {
  			return;
  		} else if (weekOfYearVisible) {
  			add(weekPanel, BorderLayout.WEST);
  		} else {
  			remove(weekPanel);
  		}
  
  		this.weekOfYearVisible = weekOfYearVisible;
  		validate();
  		dayPanel.validate();
  	}
docs: In some Countries it is often usefull to know in which week of the year a
  date is.
  
  @param weekOfYearVisible
  true, if the weeks of the year shall be shown