实时倒计时钟的问题

基本上我目前有时钟显示时间，但倒计时不工作。我从这里获得了原始代码并进行了改编。

我要做的是让倒计时从我从数据库检索到的持续时间倒数。

//TRANSFORM MYSQL TIME INTO SECONDS
    $duration_array = explode(':', $duration);
    $length = ((int)$duration_array[0] * 3600) + ((int)$duration_array[1] * 60) + (int)$duration_array[2];
    //CALCULATE FINISH TIME WITH START TIME AND DURATION.
    $target_time = $length + time();

我正在解析这个到我的JavaScript倒计时函数成功，并转换成JavaScript日期()对象。

但是目前时钟没有倒数。

这是我的javascript:

function countdown_clock(target_time)
         {
         html_code = '<div id="countdown"></div>';
         document.write(html_code);
     var timetarget = new Date(target_time *1000);
         countdown(timetarget);
         }

function countdown(timetarget)
         {
     var Today = new Date();
     Todays_Year = Today.getFullYear() - 2000;
         Todays_Month = Today.getMonth();
         //Convert both today's date and the target date into miliseconds.
         Todays_Date = (new Date(Todays_Year, Todays_Month, Today.getDate(),Today.getHours(),Today.getMinutes(),Today.getSeconds())).getTime();
     Target_Date = timetarget.getTime();
         //Find their difference, and convert that into seconds.
         Time_Left = Math.round((Target_Date - Todays_Date) / 1000);
         if(Time_Left < 0)
            Time_Left = 0;
        var innerHTML = '';
         //More datailed.
        days = Math.floor(Time_Left / (60 * 60 * 24));
        Time_Left %= (60 * 60 * 24);
        hours = Math.floor(Time_Left / (60 * 60));
        Time_Left %= (60 * 60);
        minutes = Math.floor(Time_Left / 60);
        Time_Left %= 60;
        seconds = Time_Left;
    if (seconds < 10){seconds = '0' + seconds;}
    if (minutes < 10){minutes = '0' + minutes;}
        innerHTML = hours + ':' + minutes + ':' + seconds + ' secs' ;
        document.getElementById('countdown').innerHTML = innerHTML;
         //Recursive call, keeps the clock ticking.
        setTimeout('countdown('+timetarget+');', 1000);
        }

我似乎真的很纠结于约会的事情，所以如果有任何帮助就太好了。

谢谢,