<script>
function ValidateDate(CtrlSDate,CtrlEDate)
    {
    var SDate = document.getElementById(CtrlSDate).value;    	
     var calendarDate = getCalendarDate();
 
 
    var alertReason1 =  'End Date must be greater than or equal to  Start Date.' 
 
    var endDate = new Date(calendarDate);    	
    var startDate= new Date(SDate);
 
       if(SDate != '' && EDate != '' && startDate > endDate)
    {
	    alert(alertReason1);
	    document.getElementById(CtrlEDate).value = "";
	    return false;
    }
 
}
</script>