javascript+php实现根据用户时区显示当地时间的方法

window.onload = function() {
//TODO begin 处理登陆用户时区
    //获得登陆用户时区与GMT时区的差值
    var exp = new Date();
    var gmtHours = -(exp.getTimezoneOffset()/60);
    setCookie('customer_timezone',gmtHours,1);
    //判断是否为夏令时
    date = exp.format('yyyy-MM-dd HH:mm:ss');
    if(inDaylightTime(date)){
      setCookie('inDaylightTime',1,1);
    }
}
//设置Cookie
function setCookie(c_name,value,expiredays){
    var exdate=new Date()
    exdate.setDate(exdate.getDate()+expiredays)
    document.cookie=c_name+ "=" +escape(value)+
    ((expiredays==null) ? "" : "; expires="+exdate.toGMTString())
}
//判断时间是东半球还是西半球
function isEastEarthTime(newDate)
{
  var dj= newDate.getGMTOffset(false);
  if (dj.indexOf("-") == -1){
    return true;
  } else {
    return false;
  }
}
//是否是夏令时
function inDaylightTime(date){
 var start = new Date(date.getTime());
 start.setMonth(0);
 start.setDate(1);
 start.setHours(0);
 start.setMinutes(0);
 start.setSeconds(0);
 var middle = new Date(start.getTime());
 middle.setMonth(6);
 // 如果年始和年中时差相同，则认为此国家没有夏令时
 if ((middle.getTimezoneOffset() - start.getTimezoneOffset()) == 0) 
 {
   return false;
 }
 var margin = 0;
 if (this.isEastEarthTime(date)) {
   margin = middle.getTimezoneOffset();
 } else {
   margin = start.getTimezoneOffset();
 }
 if (date.getTimezoneOffset() == margin) {
   return true;
 }
 return false;
}
//DONE end

//24小时内 GMT到本地时间的转换
function gmt_to_local($time = '', $dst = FALSE){
  //JavaScript设置Cookie,PHP取值
  if (isset($_COOKIE["customer_timezone"])){
    $timezone = $_COOKIE["customer_timezone"];
  }else{
    $timezone = 0;
  }
  if ($time == ''){
    return now();
  }
  //时间处理
  $time += $timezone  3600;
   
  //是否为夏令时
  if(isset($_COOKIE["inDaylightTime"]) && $_COOKIE["inDaylightTime"]==1)
  {
    $dst = TRUE;
  }
  if ($dst == TRUE){
    $time += 3600;
  }
  return date("H:i",$time);
}