$('#start_date').datepicker().on('changeDate', function (ev) {
  $(this).removeClass("invalid");
      $("#end_date").datepicker('setStartDate',  ev.date);



    var endingDate = new Date(ev.date);
    var endingMonth = endingDate.getMonth();
    var endingYear = endingDate.getFullYear();
    var endingDay = getDaysInMonth(endingMonth+1, endingYear);

    $("#end_date").datepicker('update', ev.date);

    endingDate = new Date(endingYear,endingMonth,endingDay);
    $("#end_date").datepicker('setEndDate',  endingDate);
    $("#end_date").datepicker('show');

    });