The following code:

      $(function(){
        $('#datepicker').datepicker({
          minDate: new Date(2009, 0, 1, 0),
          maxDate: new Date(2009, 11, 31),
          defaultDate: new Date(2009, 1, 0),
          numberOfMonths: [3,4],
          inline: true,
          changeMonth: false,
          hideIfNoPrefNext: true,
        });
      });

correctly displays a year's worth of calendars, but it shouldn't allow "next". Instead, it allows scrolling until the last month is the one in the top-right of the grid.

Looks like the "next" button disabling should use the last month in the grid, not the last month in the row.