javascript 날짜차이

<script>
var input1="20060101";
var input2="20070202";

var date1 = new Date(input1.substr(0,4),input1.substr(4,2)-1,input1.substr(6,2));
var date2 = new Date(input2.substr(0,4),input2.substr(4,2)-1,input2.substr(6,2));

var interval = date2 - date1;
var day = 1000*60*60*24;
var month = day*30;
var year = month*12;

console.log("기간 날짜수: " + parseInt(interval/day) + "일");
console.log("기간 개월수: 약 " + parseInt(interval/month) + "개월");
console.log("기간 개년수: 약 " + parseInt(interval/year) + "개년");
</script>