自行修改建站时间即可。

<div id="sitetime" style="text-align: center;"></div>
<script>
function siteTime() {
  window.setTimeout("siteTime()", 1000);
  var seconds = 1000;
  var minutes = seconds * 60;
  var hours = minutes * 60;
  var days = hours * 24;
  var years = days * 365;

  var today = new Date();
  var todayYear = today.getFullYear();
  var todayMonth = today.getMonth() + 1;
  var todayDate = today.getDate();
  var todayHour = today.getHours();
  var todayMinute = today.getMinutes();
  var todaySecond = today.getSeconds();

  var t1 = Date.UTC(2023, 1, 1, 0, 0, 0); // 北京时间2023-01-01 00:00:00创建网站的时间，修改此处的时间既是建站时间。
  var t2 = Date.UTC(todayYear, todayMonth, todayDate, todayHour, todayMinute, todaySecond);
  var diff = t2 - t1;

  var diffYears = Math.floor(diff / years);
  var diffDays = Math.floor((diff / days) - diffYears * 365);
  var diffHours = Math.floor((diff - (diffYears * 365 + diffDays) * days) / hours);
  var diffMinutes = Math.floor((diff - (diffYears * 365 + diffDays) * days - diffHours * hours) / minutes);
  var diffSeconds = Math.floor((diff - (diffYears * 365 + diffDays) * days - diffHours * hours - diffMinutes * minutes) / seconds);

  document.getElementById("sitetime").innerHTML = '数据统计：本站已上线运行 ' + diffYears + "年" + diffDays + "天" + diffHours + "小时" + diffMinutes + "分" + diffSeconds + "秒";
}

siteTime();
</script>