CRM date field

Hi I have one more question connected with the date fields. When I try to get date field's value and replace it in the other field (e.g. using odata query) I have such a problem: sometimes I get days - one day more or less.

e.g. Date_A = 20.10.2013 . I want to replase it  programmatically  in a Date_B. In Date_B I get 19.10.2013 or 21.10.2013 sometimes also 20.10.2013

//----------------------------- here is my code-------------------------------------------------------------

var EDate_close = account[0].BirthDate;

   if (EDate_close != null) { 

  var EDateVal1_close = parseInt(EDate_close.replace("/Date(", "").replace(")/", ""),10);    

   var EDateVal_close = new Date(EDateVal1_close);

       Xrm.Page.getAttribute("new_bday").setValue(EDateVal_close);        }