javascript 关于日期的

<script language="javascript">
function dayChange(YEAR,MONTH,DAY)
{

var d1=new Array(31,28,31,30,31,30,31,31,30,31,30,31);
var d2=new Array(31,29,31,30,31,30,31,31,30,31,30,31);

iYear=document.all(YEAR).value;

iMonth=document.all(MONTH).value;
if((iYear%4==0&&iYear%100==0)||(iYear%4==0&&iYear%400!=0))
{
document.all(DAY).length=d2[iMonth-1];
for(i=0;i<document.all(DAY).length;i++)
{
document.all(DAY).options[i].text=i+1;
if (i <10)
document.all(DAY).options[i].value= "0"+document.all(DAY).options[i].text;
}
}
else
{
document.all(DAY).length=d1[iMonth-1];
for(i=0;i<document.all(DAY).length;i++)
{
document.all(DAY).options[i].text=i+1;
if (i <10)
document.all(DAY).options[i].value= "0"+document.all(DAY).options[i].text;
}
}

}
</script>