Calculate time period between two dates but all the calendar day must be 30

function diff_year_month_day(dt1, dt2) 
 {
 
  var time =(dt2.getTime() - dt1.getTime()) / 1000;
  var year  = Math.abs(Math.round((time/(60 * 60 * 24))/365.25));
  var month = Math.abs(Math.round(time/(60 * 60 * 24 * 7 * 4)));
  var days = Math.abs(Math.round(time/(3600 * 24)));
  return "Year :- " + year + " Month :- " + month + " Days :-" + days;
   
 }