var xmlhttp = new ActiveXObject("MSXML2.XMLHTTP.3.0");
xmlhttp.open("GET", "https://www.bjsj5.com", false);
xmlhttp.setRequestHeader("If-Modified-Since", "bjtime");
xmlhttp.send();
var dateStr = xmlhttp.getResponseHeader("Date");
var date = new Date(dateStr);
var year = date.getFullYear();
var month = date.getMonth() + 1;
var date1 = date.getDate();
var hour = date.getHours();
var minutes = date.getMinutes();
var second = date.getSeconds();
alert(date + " | " + year + "年" + month + "月" + date1 + "日" + hour + "時" + minutes + "分" + second + "秒");