自定义年龄计算退休时间js怎么实现

最近在研究js，看到一个工具比较新颖，在线计算退休时间、退休年龄的工具，如下：http://www.chinawe.net/tools/tuixiunianling/

 

可以自定义时间和退休年龄，还能得出工作天数。

这个其实就是通过js计算出来的，下面将js代码附上

function y2k(number){
return (number < 1000) ? number + 1900 : number;
}

function daysElapsed(date1,date2){
var difference =
Date.UTC(y2k(date1.getYear()),date1.getMonth(),date1.getDate(),0,0,0)
- Date.UTC(y2k(date2.getYear()),date2.getMonth(),date2.getDate(),0,0,0);
return difference/1000/60/60/24;
}

function HowManyDays(){
var m = document.retire.MyMonth.options[document.retire.MyMonth.selectedIndex].value;
var d = document.retire.MyDay.options[document.retire.MyDay.selectedIndex].value;
var y = document.retire.MyYear.options[document.retire.MyYear.selectedIndex].value;
var birthdate = new Date(y,m,d);
var retireage = document.retire.age.options[document.retire.age.selectedIndex].value * 1;
var mo = 0;
if (retireage != Math.round(retireage)){
retireage = Math.floor(retireage);
mo = 6;
}
var retiredate = new Date(y2k(birthdate.getYear()) + retireage, birthdate.getMonth() + mo, birthdate.getDate());

var months = new Array('涓€鏈�','浜屾湀','涓夋湀',
'鍥涙湀','浜旀湀','鍏湀','涓冩湀','鍏湀','涔濇湀',
'鍗佹湀','鍗佷竴鏈�','鍗佷簩鏈�');

var day = retiredate.getDate();
var month = months[retiredate.getMonth()];
var year = y2k(retiredate.getYear());

var numdays = daysElapsed(retiredate, new Date());
document.retire.oretiredate.value = year + '骞� '+ month + ' ' + day + '鏃�';
document.retire.oretiredays.value = numdays + '澶�';
document.retire.oworkdays.value = Math.round(numdays * 5 / 7) + '澶�';
}

还有其他工具也是的，例如

安全期计算器