js实现倒计时的小例子

<html>
<head>
<title>Xinyu2008年生日的倒计时测试</title>
<b>今天距离2008年8月2日ZM的生日还有</b><br>
<script language="JavaScript">

<!-- 隐藏脚本从旧的浏览器
var DifferHour = -1
var DifferMinute = -1
var DifferSecond = -1
var Tday1 = new Date("Aug 2, 2008 20:00:00")   //**倒计时时间-注意格式
var daysms = 24 * 60 * 60 * 1000
var hoursms = 60 * 60 * 1000
var Secondms = 60 * 1000
var microsecond = 1000
function clock()
{
    var time = new Date()
    var hour = time.getHours()
    var minute = time.getMinutes()
    var second = time.getSeconds()
    var timevalue = ""+((hour > 12) ? hour-12:hour)
    timevalue +=((minute < 10) ? ":0":":")+minute
    timevalue +=((second < 10) ? ":0":":")+second
    timevalue +=((hour >12 ) ? " PM":" AM")
    var convertHour = DifferHour
    var convertMinute = DifferMinute
    var convertSecond = DifferSecond
    var Diffms = Tday1.getTime() - time.getTime()
    DifferHour = Math.floor(Diffms / daysms)
    Diffms -= DifferHour * daysms
    DifferMinute = Math.floor(Diffms / hoursms)
    Diffms -= DifferMinute * hoursms
    DifferSecond = Math.floor(Diffms / Secondms)
    Diffms -= DifferSecond * Secondms
    var dSecs = Math.floor(Diffms / microsecond)
    if(convertHour != DifferHour) document.formnow.dd.value=DifferHour
    if(convertMinute != DifferMinute) document.formnow.hh.value=DifferMinute
    if(convertSecond != DifferSecond) document.formnow.mm.value=DifferSecond
        document.formnow.ss.value=dSecs
        document.formnow.ss.value=dSecs
// document.formnow.Tnow.value= DifferHour DifferMinute + DifferSecond + dSecs
setTimeout("clock()",1000)

}
//

隐藏-->
</script>
</head>
<body onload="clock();return true" text="red">

<form name="formnow">
<input name="dd" type="text" style="border:0;" size=2>
天
<input name="hh" type="text" style="border:0;" size=2>
小时
<input name="mm" type="text" style="border:0;" size=2>
分
<input name="ss" type="text" style="border:0;" size=2>
秒
</form>

</body>
</html>