javascriptで北京の標準時間

<b>北京の標準時間</b>
<div id="time"></div>
<script type="text/javascript">
var diff = 1;
var value = diff + 15;
time();
function time(){
  var now = new Date(Date.now() - (value*60 - new Date().getTimezoneOffset())*60000);
  document.getElementById("time").innerHTML = now.toLocaleTimeString();
}
setInterval('time()', 1000);
</script>