<form name=form1>

<select name=YYYY onchange="YYYYMM(this.value)">

<option value="">請選擇 年</option>

</select>

<select name=MM onchange="MMDD(this.value)">

<option value="">選擇 月</option>

</select>

<select name=DD>

<option value="">選擇 日</option>

</select>

</form>

<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];

//先給年下拉框賦內(nèi)容

var y = new Date().getFullYear();

var str = strYYYY.substring(0, strYYYY.length - 9);

for (var i = (y-30); i < (y+30); i++) //以今年為準(zhǔn)，前30年，后30年

{

str += "<option value='" + i + "'> " + i + " 年" + "</option>\r\n";

}

document.form1.YYYY.outerHTML = str +"</select>";

//賦月份的下拉框

var str = strMM.substring(0, strMM.length - 9);

for (var i = 1; i < 13; i++)

{

str += "<option value='" + i + "'> " + i + " 月" + "</option>\r\n";

}

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); //賦日期下拉框

document.form1.DD.value = new Date().getDate();

}

function YYYYMM(str) //年發(fā)生變化時日期發(fā)生變化(主要是判斷閏平年)

{

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) //月發(fā)生變化時日期聯(lián)動

{

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) //據(jù)條件寫日期的下拉框

{

var s = strDD.substring(0, strDD.length - 9);

for (var i=1; i<(n+1); i++)

s += "<option value='" + i + "'> " + i + " 日" + "</option>\r\n";

document.form1.DD.outerHTML = s +"</select>";

}

function IsPinYear(year)//判斷是否閏平年

{ return(0 == year%4 && (year%100 !=0 || year%400 == 0))}

//--></script>

注意紅色字體！