Con el siguiente codigo podras agregar un muy bonito calendario en tu web.

<SCRIPT language="javascript">
function getmon(m0, m1, m2, m3, m4, m5, m6, m7, m8, m9, m10, m11)
{this[0] = m0;this[1] = m1;this[2] = m2;this[3] = m3;this[4] = m4;this[5] =  	m5;
this[6] = m6;this[7] = m7;this[8] = m8;this[9] = m9;
this[10] = m10;this[11] = m11;}function calendar(){
var monthNames = "EneFebMarAbrMayJunJulAgoSepOctNovDic";
var today = new Date();var thisDay;
var monthDays = new getmon(31, 28, 31, 30, 31, 30, 31, 31, 30,
31, 30, 31);year = today.getFullYear();thisDay = today.getDate();
if (((year % 4 == 0) &amp;&amp; (year % 100 != 0)) || (year % 400 == 0))
monthDays[1] = 29;nDays = monthDays[today.getMonth()];
firstDay = today;firstDay.setDate(1);startDay = firstDay.getDay();
document.writeln("<center>");
document.write("<table border=0 cellpadding=0><font size=1pt>");
document.write("<tr><th colspan=0><font size=1pt>");
document.write(monthNames.substring(today.getMonth() * 3,
(today.getMonth() + 1) * 3));document.write(". ");
document.write(year);document.write("<tr><th>");document.write
("Dom<th>Lun<th>Mar<th>Mié<th>Jue<th>Vie<th>Sáb");
document.write("<tr>");column = 0;for (i=0; i<startDay; i++){
document.write("<td align=center><font size+=3>");column++;
document.write("</font>");}for (i=1; i<=nDays; i++){
document.write("<td align=center>");if (i == thisDay)
document.write("<font color=\"#FFd700\" size+=3><b>")
document.write(i);if (i == thisDay)document.write("</font></b>")
column++;if (column == 7){document.write("<tr>");column = 0;
}}document.write("</table>");}calendar();document.write();
function shutdown(){window.close()}// –></SCRIPT>