网站底部添加网站运行时间代码，自动计算精确到秒

<span id="runtime_span"></span> <script type="text/javascript"> function show_runtime() {window.setTimeout("show_runtime()",1000); X=new Date("10/16/2017 5:22:00"); Y=new Date(); T=(Y.getTime()-X.getTime()); M=24*60*60*1000; a=T/M;A=Math.floor(a); b=(a-A)*24;B=Math.floor(b); c=(b-B)*60;C=Math.floor((b-B)*60); D=Math.floor((c-C)*60); runtime_span.innerHTML="本站勉强运行: "+A+"天"+B+"小时"+C+"分"+D+"秒"}show_runtime(); </script> Date("10/16/2017 5:22:00")