How to compare DateTime

function Datevalidate(txtFromdate,txtToDate)
{

   var txtFromdate = document.getElementById(txtFromdate);
   var txtToDate = document.getElementById(txtToDate);

   if(txtFromdate.value!="" || txtToDate.value!="")
  {
        var str1 = txtFromdate.value;
        var str2 = txtToDate.value;
        var dt1  = parseInt(str1.substring(0,2),10);
        var mon1 = parseInt(str1.substring(3,5),10);
        var yr1  = parseInt(str1.substring(6,10),10);
        var dt2  = parseInt(str2.substring(0,2),10);
        var mon2 = parseInt(str2.substring(3,5),10);
        var yr2  = parseInt(str2.substring(6,10),10);
        var date1 = new Date(yr1, mon1, dt1);
        var date2 = new Date(yr2, mon2, dt2);     
        if(date2 < date1)
        {
            alert("To Date cannot be lesser than From Date");
            return false;
        }  
    }
}