<div>
<select name="YYYY" onchange="YYYYMM(this.value)">
<option value=""> Please select a years </option>
</select>
<select name="MM" onchange="MMDD(this.value)">
<option value=""> choose month </option>
</select>
<select name="DD">
<option value=""> choose day </option>
</select>
</div>
<script language="JavaScript">
function window.onload() {
strYYYY = document.form1.YYYY.outerHTML;
strMM = document.form1.MM.outerHTML;
strDD = document.form1.DD.outerHTML;
MonHead = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
//First give the contents of the year drop - down box
var y = new Date().getFullYear();
var str = strYYYY.substring(0, strYYYY.length - 9);
for (var i = (y - 30); i < (y + 30); i++) //This year shall prevail, the first 30 years and the last 30 years
{
str += "<option value='" + i + "'> " + i + " years " + "</option>rn";
}
document.form1.YYYY.outerHTML = str + "</select>";
//The drop-down box for the assigned month
var str = strMM.substring(0, strMM.length - 9);
for (var i = 1; i < 13; i++) {
str += "<option value='" + i + "'> " + i + " month " + "</option>rn";
}
document.form1.MM.outerHTML = str + "</select>";
document.form1.YYYY.value = y;
document.form1.MM.value = new Date().getMonth() + 1;
var n = MonHead[new Date().getMonth()];
if (new Date().getMonth() == 1 && IsPinYear(YYYYvalue)) n++;
writeDay(n); //Assign date drop-down box
document.form1.DD.value = new Date().getDate();
}
function YYYYMM(str) //When the year changes, the date changes (mainly to judge the run-flat year)
{
var MMvalue = document.form1.MM.options[document.form1.MM.selectedIndex].value;
if (MMvalue == "") { DD.outerHTML = strDD; return; }
var n = MonHead[MMvalue - 1];
if (MMvalue == 2 && IsPinYear(str)) n++;
writeDay(n)
}
function MMDD(str) //Date linkage when month changes
{
var YYYYvalue = document.form1.YYYY.options[document.form1.YYYY.selectedIndex].value;
if (str == "") { DD.outerHTML = strDD; return; }
var n = MonHead[str - 1];
if (str == 2 && IsPinYear(YYYYvalue)) n++;
writeDay(n)
}
function writeDay(n) //A drop-down box that conditionally writes the date
{
var s = strDD.substring(0, strDD.length - 9);
for (var i = 1; i < (n + 1); i++)
s += "<option value='" + i + "'> " + i + " day " + "</option>rn";
document.form1.DD.outerHTML = s + "</select>";
}
function IsPinYear(year)//Judge whether a leap year
{
return (0 == year % 4 && (year % 100 != 0 || year % 400 == 0))
}