也挺简单，我也是小白，把下面代码复制一下

<!-- 开站时间开始 --><span id="timeDate">载入天数...</span><span id="times">载入时分秒...</span> <script language="javascript"> 
    var now = new Date();
    function createtime(){
        var grt= new Date("04/17/2022 00:00:00");/*---这里是网站的启用时间--*/
        now.setTime(now.getTime()+250);
        days = (now - grt ) / 1000 / 60 / 60 / 24;
        dnum = Math.floor(days);
        hours = (now - grt ) / 1000 / 60 / 60 - (24 * dnum);
        hnum = Math.floor(hours);
        if(String(hnum).length ==1 ){hnum = "0" + hnum;}
        minutes = (now - grt ) / 1000 /60 - (24 * 60 * dnum) - (60 * hnum);
        mnum = Math.floor(minutes);
        if(String(mnum).length ==1 ){mnum = "0" + mnum;}
        seconds = (now - grt ) / 1000 - (24 * 60 * 60 * dnum) - (60 * 60 * hnum) - (60 * mnum);
        snum = Math.round(seconds);
        if(String(snum).length ==1 ){snum = "0" + snum;}
        document.getElementById("timeDate").innerHTML = "本站已稳定运行"+dnum+"天";
        document.getElementById("times").innerHTML = hnum + "小时" + mnum + "分" + snum + "秒";
    }
    setInterval("createtime()",250); 
</script> <!-- 开站时间结束 -->

然后去宝塔-网站根目录

打开footer.php-拉到下面，我是把版权删了换成了这个，你们可以保留作者版权。
粘贴上之后改一下时间即可。

是不是很简单...