$(document).ready(function () {

    var columns = [

    {

        field: "Activity_M().StartTime_M()",

        title: "StartTime <br/> <input type='text' id='filterStartTime' style='width:100px;' autocomplete='off'/>",

        width: 150,

        format: Date.CultureInfo.formatPatterns.shortDate,

        editor: "<input data-bind='ActivityTimeBinder:Activity_M().StartTime_M' />"

    }];

    var dt = Date.today();

    $filterStartTime.datepicker({

        onClose: function (dateText, inst) {

            var isValidDate = $filterStartTime.datepicker("getDate");

            if (isValidDate == null) {

                ganttControl.ResetFilters();

            }

            else {

                $gantt_container.GanttControl({ FilterActivites: StartDateFilter });

                ganttControl.Filter();

            }

        }

    }).datepicker('setDate', dt);

   function StartDateFilter(activity) {

         // Your comparison code comes here.

        if (activity.StartTime.compareTo(filterDate) == 0)

            return true; // To include

        return false; // To exclude

     }

});