jquery時間計時器

//從之前的某個時間段到現在距離多少天多少時多少分多少秒
<div id="times_wrap" class="time_num"> 
    //距離現在時間
    <div class="time_w"> 
        <span id="time_d" class="time"> </span >天 
        <span id="time_h" class="time"> </span >時 
        <span id="time_m" class="time"> </span >分 
        <span id="time_s" class="time"> </span >秒 
    </div>
</div> 
<script type="text/javascript"> 
    $(function(){ 
        show_time(); 
    }); 
    function show_time(){ 
        var time_start = new Date("2013/10/01 00:00:00").getTime();//設定開始時間 
        var time_end = new Date().getTime(); //設定結束時間(等於系統當前時間) 
        //計算時間差 
        var time_distance = time_end - time_start; 
        if(time_distance > 0){ 
            // 天時分秒換算 
            var int_day = Math.floor(time_distance/86400000) 
            time_distance -= int_day * 86400000; 
            
            var int_hour = Math.floor(time_distance/3600000) 
            time_distance -= int_hour * 3600000; 
            
            var int_minute = Math.floor(time_distance/60000) 
            time_distance -= int_minute * 60000; 
            
            var int_second = Math.floor(time_distance/1000) 
            // 時分秒爲單數時、前面加零 
            if(int_day < 10){ 
                int_day = "0" + int_day; 
            } 
            if(int_hour < 10){ 
                int_hour = "0" + int_hour; 
            } 
            if(int_minute < 10){ 
                int_minute = "0" + int_minute; 
            } 
            if(int_second < 10){ 
                int_second = "0" + int_second; 
            } 
            // 顯示時間 
            $("#time_d").html(int_day); 
            $("#time_h").html(int_hour); 
            $("#time_m").html(int_minute); 
            $("#time_s").html(int_second); 
            setTimeout("show_time()",1000); 
        }else{ 
            $("#time_d").html('00'); 
            $("#time_h").html('00'); 
            $("#time_m").html('00'); 
            $("#time_s").html('00'); 
        } 
    } 
</script>