如何使用 JavaScript 了解一个国家/地区是否使用夏令时？

Question

我在中国，我有一个朋友在其他国家。例如英国、美国、新西兰...

我知道他的国家的英文名称和时区。

但我怎么知道他的国家现在是否实行夏令时呢？有什么想法吗？

谢谢你！

Answer 1

以下是使用 JSONP 和一些 Yahoo 服务的示例：

function jsonp(src){
        var s = document.createElement('script');
    s.charset = 'UTF-8';
    document.body.appendChild(s);
    s.src = src;
}
function getLocation(where){
    var src = 'http://query.yahooapis.com/v1/public/yql?callback=getTimeZone' + 
        '&q=select%20*%20from%20geo.places%20where%20text="'+ where +
        '"&format=json';
    jsonp(src);
}
function getTimeZone(response){
    var location = response.query.results.place[0].centroid, 
        src = 'http://query.yahooapis.com/v1/public/yql?callback=showTz' + 
        '&q=select%20*%20from%20xml%20where%20url%3D"http%3A%2F%2Fws.geonames.org%2Ftimezone%3Flat%3D' + 
        location.latitude +'%26lng%3D' +
        location.longitude + '"&format=json';
    jsonp(src);
}
function showTz(tz){
    console.log(tz.query.results.geonames.timezone);
}
getLocation('paris');

Answer 2

检查这个脚本可能对你有帮助。参考：http://www.irt.org/< /strong>

<SCRIPT LANGUAGE="JavaScript"><!--
function makeArray()    {
    this[0] = makeArray.arguments.length;
    for (i = 0; i<makeArray.arguments.length; i++)
        this[i+1] = makeArray.arguments[i];
}

var daysofmonth   = new makeArray( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
var daysofmonthLY = new makeArray( 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

function LeapYear(year) {
    if ((year/4)   != Math.floor(year/4))   return false;
    if ((year/100) != Math.floor(year/100)) return true;
    if ((year/400) != Math.floor(year/400)) return false;
    return true;
}

function NthDay(nth,weekday,month,year) {
    if (nth > 0) return (nth-1)*7 + 1 + (7 + weekday -
DayOfWeek((nth-1)*7 + 1,month,year))%7;
    if (LeapYear(year)) var days = daysofmonthLY[month];
    else                var days = daysofmonth[month];
    return days - (DayOfWeek(days,month,year) - weekday + 7)%7;
}

function DayOfWeek(day,month,year) {
    var a = Math.floor((14 - month)/12);
    var y = year - a;
    var m = month + 12*a - 2;
    var d = (day + y + Math.floor(y/4) - Math.floor(y/100) +
Math.floor(y/400) + Math.floor((31*m)/12)) % 7;
    return d+1;
}

function y2k(number)    { return (number < 1000) ? number + 1900 : number; }

var today = new Date();
var year = y2k(today.getYear());

var DSTstart = new Date(year,4-1,NthDay(1,1,4,year),2,0,0);
var DSTend   = new Date(year,10-1,NthDay(-1,1,10,year),2,0,0);

function getMS(date) {
    return
Date.UTC(y2k(date.getYear()),date.getMonth(),date.getDate(),date.getHours(),date.getMinutes(),date.getSeconds())
}

var todayMS = getMS(today);
var DSTstartMS = getMS(DSTstart);
var DSTendMS = getMS(DSTend);

if (todayMS > DSTstartMS && todayMS < DSTendMS)
    document.write('Daylight Saving within effect');
else
    document.write('Daylght Saving NOT within effect');
//--></SCRIPT>

Answer 3

好吧，我只是拼凑了这段代码来确定当前选择的时区是否使用夏季调整以及当前是否有效。这是为 Windows Scripting Host 编写的，但可以将 WScript.Echo 替换为 window.alert 或您喜欢的任何环境，以适应您选择运行它的环境...

// Solstice dates are approximate here!
// Don't give me grief about it varying from year to year.

var juneSolstice = new Date();
juneSolstice.setMonth(5); // zero-based
juneSolstice.setDate(21);

var decemberSolstice = new Date();
decemberSolstice.setMonth(11); // zero-based
decemberSolstice.setDate(21);

var now = new Date();

WScript.Echo(juneSolstice.getTimezoneOffset());
WScript.Echo(decemberSolstice.getTimezoneOffset());

var winterOffset = Math.max(juneSolstice.getTimezoneOffset(), decemberSolstice.getTimezoneOffset())
var summerOffset = Math.min(juneSolstice.getTimezoneOffset(), decemberSolstice.getTimezoneOffset())

if (juneSolstice.getTimezoneOffset() != decemberSolstice.getTimezoneOffset())
{
    WScript.Echo("This time zone uses summer time adjustment.");
}

if (now.getTimezoneOffset() != winterOffset)
{
    WScript.Echo("Summer time is currently in effect.");
}
else
{
    WScript.Echo("Summer time is currently NOT in effect.");
}