How to compare two dates and How to Know Sunday on the particular date

function todaydate()

    {

    debugger;

        var Todaydate =new Date() ;

        var TextBoxDate=document.getElementById("TxtDate").value;

        var currentDate = new Date()

        var day = currentDate.getDate()

        var month = currentDate.getMonth() + 1

        var year = currentDate.getFullYear()

       

        if (TextBoxDate.length < 10)

        {

         alert('Please Enter Correct Date!');

         return false;

        }

       

        if (month < 10)

            {

                Todaydate= ("0" + month + "/" + day + "/" +  year) ;

            }

        else

            {

                Todaydate= (month + "/" + day + "/" +  year) ;

            }       

        var ConvertTodayDate= Date.parse (Todaydate);       

        var date1 = new Date(ConvertTodayDate)    

    

        var day1 = TextBoxDate.substring(0,2);

        var month1 = TextBoxDate.substring(4,5);

        var year1 = TextBoxDate.substring(6,10);

    

      if (month1 < 10)

            {

                TextBoxDate= ("0" + month1 + "/" + day1 + "/" +  year1) ;

            }

        else

            {

                TextBoxDate= (month1 + "/" + day1 + "/" +  year1) ;

            }

           

       var  ConvertTextBoxDate= Date.parse (TextBoxDate);

       var date2 = new Date(ConvertTextBoxDate)

      if (date2  < date1)

        {

        alert("Order cannot be booked for same day and back day !");

            return false

        }

     

       if (Todaydate == TextBoxDate)

         {

            alert("Order cannot be booked for same day and back day !");

            return false

         }

        //Given Below Line for Getting Sunday

        var forsunday = date2.getDay(); 

        if (forsunday == 0)

         {

        alert("Order cannot be booked for Sunday!");

        return false

         } 

        

         if(document.form1.DDlDelTime.selectedIndex==0)

         {

         alert('Please Select Delivery Time. !')

        

         return false;

         }

        

      var IISHours = document.getElementById("LblHours").innerHTML;

      var Min = document.getElementById("LblMin").innerHTML;

      var IISDate = document.getElementById("LblDate").innerHTML;

      TextBoxDate=document.getElementById("TxtDate").value;

        if (IISDate == TextBoxDate)

        {

                if (IISHours > 22 && Min > 0)

                {

                alert('Order cannot be booked for Tomorrow after 10 PM.');

                return false;

                }

        }  

}