<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
</HEAD>
<BODY>
<script language="JavaScript">
TargetDate = "1/1/2009 00:00 AM";
BackColor = "white";
ForeColor = "navy";
CountActive = true;
CountStepper = -1;
LeadingZero = true;
DisplayFormat = "เหลือเวลาอีก %%D%% วัน, %%H%% ชั่วโมง, %%M%% นาที, %%S%% วินาที. ก็ปีใหม่แล้ว";
FinishMessage = "It is finally here!";
function calcage(secs, num1, num2) {
s = ((Math.floor(secs/num1))%num2).toString();
if (LeadingZero && s.length < 2)
s = "0" + s;
return "<b>" + s + "</b>";
}
function CountBack(secs) {
if (secs < 0) {
document.getElementById("cntdwn").innerHTML = FinishMessage;
return;
}
DisplayStr = DisplayFormat.replace(/%%D%%/g, calcage(secs,86400,100000));
DisplayStr = DisplayStr.replace(/%%H%%/g, calcage(secs,3600,24));
DisplayStr = DisplayStr.replace(/%%M%%/g, calcage(secs,60,60));
DisplayStr = DisplayStr.replace(/%%S%%/g, calcage(secs,1,60));
document.getElementById("cntdwn").innerHTML = DisplayStr;
if (CountActive)
setTimeout("CountBack(" + (secs+CountStepper) + ")", SetTimeOutPeriod);
}
function putspan(backcolor, forecolor) {
document.write("<span id='cntdwn' style='background-color:" + backcolor +
"; color:" + forecolor + "'></span>");
}
if (typeof(BackColor)=="undefined")
BackColor = "white";
if (typeof(ForeColor)=="undefined")
ForeColor= "black";
if (typeof(TargetDate)=="undefined")
TargetDate = "12/31/2020 5:00 AM";
if (typeof(DisplayFormat)=="undefined")
DisplayFormat = "%%D%% Days, %%H%% Hours, %%M%% Minutes, %%S%% Seconds.";
if (typeof(CountActive)=="undefined")
CountActive = true;
if (typeof(FinishMessage)=="undefined")
FinishMessage = "";
if (typeof(CountStepper)!="number")
CountStepper = -1;
if (typeof(LeadingZero)=="undefined")
LeadingZero = true;
CountStepper = Math.ceil(CountStepper);
if (CountStepper == 0)
CountActive = false;
var SetTimeOutPeriod = (Math.abs(CountStepper)-1)*1000 + 990;
putspan(BackColor, ForeColor);
var dthen = new Date(TargetDate);
var dnow = new Date();
if(CountStepper>0)
ddiff = new Date(dnow-dthen);
else
ddiff = new Date(dthen-dnow);
gsecs = Math.floor(ddiff.valueOf()/1000);
CountBack(gsecs);
</script>
</BODY>
</HTML>
ลองเอาไปดัดแปลงต่อดูนะครับ
ปล. ผมเอาของ เว็บนี้มาแก้ไขหน่ะครับ ให้ credit เค้าซะหน่อย
http://www.hashemian.com/tools/javascript-countdown.htm 
พัฒนาเว็บไซต์
