code: private void setSizeOfWeekNumberLabels() {
          JLabel firstLabel = weekNumberLabels.get(0);
          Font font = firstLabel.getFont();
          FontMetrics fontMetrics = firstLabel.getFontMetrics(font);
          int width = fontMetrics.stringWidth("53 ");
          width += constantWeekNumberLabelInsets.left;
          width += constantWeekNumberLabelInsets.right;
          Dimension size = new Dimension(width, 1);
          for (JLabel currentLabel : weekNumberLabels) {
              currentLabel.setMinimumSize(size);
              currentLabel.setPreferredSize(size);
          }
          topLeftLabel.setMinimumSize(size);
          topLeftLabel.setPreferredSize(size);
      }
docs: setSizeOfWeekNumberLabels, This sets the minimum and preferred size of the week number
  labels, to be able to hold largest week number in the current week number label font.
  
  Note: The week number labels need to be added to the panel before this method can be called.