javascript获取服务器时间

<span style="font-size:14px;">function getServerTime(){
var xmlHttp = false;
//获取服务器时间
try {
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e2) {
xmlHttp = false;
}
}
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
xmlHttp = new XMLHttpRequest();
}
xmlHttp.open("GET", "http://xxx.xxx.xxx.xxx/getTime/", false);
xmlHttp.setRequestHeader("Range", "bytes=-1");
xmlHttp.send(null);
var severtime = (new Date(xmlHttp.getResponseHeader("Date"))).getTime();
return severtime;
}</span>