code: private void setSizeOfDatePanelCell() {
          // Skip this function if the settings have not been applied.
          if (settings == null) {
              return;
          }
          // Get the minimum desired size of the date panel.
          int minimumHeight = settings.getSizeDatePanelMinimumHeight();
          int minimumWidth = settings.getSizeDatePanelMinimumWidth();
          // Get the layout for the calendar panel.
          GridBagLayout layout = ((GridBagLayout) getLayout());
          // Initialize the minimum height and width of the date panel cell.
          int panelHeight = minimumHeight;
          int panelWidth = minimumWidth;
          // Force the new size to be multiples of 7 for the columns and rows.
          panelHeight += (panelHeight % 7);
          panelWidth += (panelWidth % 7);
          // Set the containing cell to be the desired minimum size.
          layout.rowHeights[3] = panelHeight + constantSizeOfCenterPanelBorders.height;
          layout.columnWidths[1] = panelWidth + constantSizeOfCenterPanelBorders.width;
          // Ask the components to layout and redraw themselves.
          this.doLayout();
          this.validate();
      }
docs: setSizeOfDatePanelCell, This sets the size of the cell that holds the date panel. By default,
  the size is set in such a way that the grid layout of the date panel will always touch the
  inside edges of the cell. At the time of this writing, the cell that contains the date panel
  is: x=1, y=3, in the calendar panel.