怎么在form中动态添加select(有关日历)

<html>
<head>
<title>无标题文档</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<script language=javascript>
function datetimesel(){
theDateTime=new Date();
theYear=document.form1.year;
theMonth=document.form1.month;
theHour=document.form1.hour;
theMinute=document.form1.minute;
//getYear
for(i=0;i<5;i++){
theYear.options[i]=new Option(theDateTime.getYear()+i,theDateTime.getYear()+i);
theYear.options[0].select=true;
}
//getMonth
for(i=1;i<13;i++){
theMonth.options[i-1]=new Option(i,i);
if(theDateTime.getMonth()+1==i) theMonth.options[i-1].selected=true;
}
//getDay
getThatDay(theDateTime.getYear(),theDateTime.getMonth()+1);
//getHour
for(i=0;i<24;i++){
theHour.options[i]=new Option(i,i);
if(theDateTime.getHours()==i) theHour.options[i].selected=true;
}
//getMinute
for(i=0;i<60;i++){
theMinute.options[i]=new Option(i,i);
if(theDateTime.getMinutes()==i) theMinute.options[i].selected=true;
}
}function getThatDay(thatYear,thatMonth){
theDateTime=new Date();
theDay=document.form1.day;
for(i=0;i<theDay.options.length;i++){
theDay.options[i]=null;
}
for(i=1;i<getMaxDay(thatYear,thatMonth)+1;i++){
theDay.options[i-1]=new Option(i,i);
if(theDateTime.getDate()==i) theDay.options[i-1].selected=true;
}
}function getMaxDay(thatYear,thatMonth){
var thatMaxDay = [31,28,31,30,31,30,31,31,30,31,30,31];
    if (thatYear%4==0) thatMaxDay[1] = 29;
    return thatMaxDay[thatMonth-1];
}
</script>
<style type="text/css">
<!--
.input {  color: #FF0000; background-color: #CCCCbf; border: #000000; border-style: solid; border-top-width: 1px; border-right-width: 1px; border-bottom-width: 1px; border-left-width: 1px}
-->
</style>
</head><body bgcolor="#FFFFFF" text="#000000" onLoad="datetimesel();">
<form name="form1" method="post" action="">
  <select name="year" onChange="getThatDay(this.value,month.value);" class="input">
  </select>
  年
  <select name="month" onChange="getThatDay(year.value,this.value);" class="input">
  </select>
  月
  <select name="day" class="input">
  </select>
  日
  <select name="hour" class="input">
  </select>
  时
  <select name="minute" class="input">
  </select>
  分
  </form>
</body>
</html>
我也写了一个差不多的，你看看能不能用