calendar.css:
.cal {
background-color: #ffffff;
}

.head {
color: #bb0000;
font-family: Arial;
font-weight: bold;
text-align: left;
}

.days {
color: #0000bb;
font-family: Arial;
font-weight: bold;
text-align: right;
}

.grey {
color: #ffffff;
font-family: Arial;
font-size: small;
text-align: right;
}

.links {
color: #ff0000;
font-family: Arial;
font-size: small;
text-align: right;
}

.today {
color: #ffffff;
background-color: #ff0000;
font-family: Arial;
font-size: small;
text-align: right;
}

calendar.js:
January,February,March,
April,May,June,July,
August,September,October,
November,December
);

var daysOfMonth = new Array(
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
);

var daysOfMonthLY = new Array(
31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
);

var dow = new Array(Sun,Mon,Tue,Wed,Thu,Fri,Sat,
Sun,Mon,Tue,Wed,Thu,Fri);

var size = width="50" height="30";
var border = border="1";

function isLeapYear(num) {
if (((num % 4 == 0) && (num % 100 != 0)) || (num % 400 == 0))
return true;
return false;
}

function CalendarSelect(Month,Year, offset) {
if (offset == null) offset = 0;

if (window.changeMonth) { }
else {
alert(A changeMonth() function has not been defined);
return ;
}

if (window.changeYear) { }
else {
alert(A changeYear() function has not been defined);
return ;
}

if (window.changeDay) { }
else {
alert(A changeDay() function has not been defined);
return ;
}

var output = ;

output += <form name="Cal">;
output += CalendarHead(Month,Year,true);
output += CalendarMonth(Month,Year,offset);
output += </form>;

return output;
}

function CalendarHead(Month,Year,Select) {
var output = ;

output +=
<table cellspacing="0" class="cal"> +
<tr><td align="left" width="100%" class="head"> +
moy[Month-1] + + Year +
</td>;

if (Select) {

output += <td width="50%" align="right"> +
<select name="Month" onChange="CalMonth()">;

for (var month=1; month<=12; month++) {
output += <option value=" + month + ";
if (month == Month) output += selected;
output += > + moy[month-1] + </option>;
}

output += </select> +
<select name="Year" onChange="CalYear();">;

for (var year=1900; year<=2100; year++) {
output += <option value=" + year + ";
if (year == Year) output += selected;
output += > + year + </option>;
}

output += </select>;
}

output += </td></tr></table>;

return output;
}

function CalendarMonth(M,Y,offset) {
M--;
if (offset == null) offset = 0;

firstDay = new Date(Y,M,1);
startDay = firstDay.getDay();

if (startDay < offset) startDay += 7;

var days = daysOfMonth;
if (isLeapYear(Y)) days = daysOfMonthLY;

var output = ;

output +=
<table + border + cellpadding="0" class="cal"><tr>;

for (var i=0; i<7; i++)
output += <td + size + class="days"> +
dow[i + offset] + </td>;

output += </tr><tr>;

var column = 0;
var lastM = M - 1;
if (lastM == -1) lastM = 11;

for (var i=0+offset; i<startDay; i++, column++)
output += <td + size + class="grey"> +
(days[lastM]-startDay+i+1) + </td>;

for (var i=1; i<=days[M]; i++, column++) {
var style = class="links";
if (day == i && month == M+1 && year == Y)
style = class="today";
if (window.changeDay)
output += <td + size + > +
<a href="javascript:CalDay(+i+,+(M+1)+,+Y+)" +
style + > + i + </a></td>;
else
output += <td + size + style + > + i + </td>;

if (column == 6) {
output += </tr><tr>;
column = -1;
}
}

if (column > 0) {
for (var i=1; column<7; i++, column++)
output += <td + size + class="grey"> + i + </td>;
}

output += </tr></table>;

return output;
}

function getAnOptionValue(what) {
return what.options[what.options.selectedIndex].value;
}

function CalMonth() {
CalendarMonth = getAnOptionValue(document.Cal.Month) - 0;
changeMonth(CalendarMonth);
}

function CalYear() {
CalendarYear = getAnOptionValue(document.Cal.Year) - 0;
changeYear(CalendarYear);
}

function CalDay(day,month,year) {
CalendarDay = day;
CalendarMonth = month;
CalendarYear = year;
changeDay(CalendarDay,CalendarMonth,CalendarYear);
}

var CalendarMonth;
var CalendarYear;
var CalendarDay;

current.js:
function getFullYear() {
var year = this.getYear();
if (year < 1000) year += 1900;
return year;
}

if (!Date.getFullYear)
Date.prototype.getFullYear = getFullYear;

function getMilliseconds() {
var date = new Date(
this.getFullYear(), this.getMonth(), this.getDate(),
this.getHours(), this.getMinutes(), this.getSeconds(), 0
);
return this.getTime() - date.getTime();
}

if (!Date.getMilliseconds)
Date.prototype.getMilliseconds = getMilliseconds;

var daysOfWeek = new Array(
Sunday,Monday,Tuesday,Wednesday,
Thursday,Friday,Saturday
);

var monthsOfYear = new Array(
January,February,March,April,May,June,
July,August,September,October,November,December
);

function y2k(number) {
number = number - 0;
return (number < 1000) ? number + 1900 : number;
}

function dayOfWeek(day,month,year) {
var a = Math.floor((14 - month)/12);
var y = year - a;
var m = month + 12*a - 2;
var d = (day + y + Math.floor(y/4) - Math.floor(y/100) +
Math.floor(y/400) + Math.floor((31*m)/12)) % 7;
return d;
}

function nths(day) {
if (day == 1 || day == 21 || day == 31) return st;
if (day == 2 || day == 22) return nd;
if (day == 3 || day == 23) return rd;
return th;
}

function formatFullDate(day,month,year) {
var dow = dayOfWeek(day,month,year);
return daysOfWeek[dow] + +
day + nths(day) + +
monthsOfYear[month-1] + + year;
}

function padout(num) {
return (num < 10) ? 0 + num : num;
}

function formatShortDate(day,month,year) {
return padout(day) + / + padout(month) + / + year;
}

function formatShortDateUS(day,month,year) {
return padout(month) + / + padout(day) + / + year;
}

index.htm:
<html>

<head>

<title>Calendar</title>

<link rel="stylesheet" href="calendar.css" type="text/css">

<script language="JavaScript" src="current.js"></script>
<script language="JavaScript" src="calendar.js"></script>

</head>

<body bgcolor="#ffffff">

<center>

<script language="JavaScript"><!--
size = ;
border = border="0";
dow = new Array(S,M,T,W,T,F,S,
S,M,T,W,T,F);
moy = new Array(
Jan,Feb,Mar,Apr,May,Jun,
Jul,Aug,Sep,Oct,Nov,Dec
);

function changeDay(day, month, year) {
alert(new Date(year, month, day));
}

var output = ;

if (window.formatFullDate && window.CalendarSelect) {
var today = new Date();
var day = today.getDate();
var month = today.getMonth() + 1;
var year = today.getFullYear();

output +=
<table class="cal" border="1"><tr><td valign="top">;

for (var i = 1; i <= 12; i++) {
output += <table><tr><td> +
CalendarHead(i,year) +
CalendarMonth(i,year,1) +
</td></tr></table>;

if (i != 12) {
if (i % 3 == 0)
output += </td></tr><tr><td valign="top">;
else
output += </td><td valign="top">;
}
}

output += </td></tr></table>;
}

document.write(output);
//--></script>

</center>

</body>

</html>

把这四个文件放在同一目录下。运行index.htm