c# - 检查夏令时是否有效？

Question

如何检查丹麦夏令时是否生效，如果是，则在我的数据中添加 1 小时，否则不是？我有一个 xml 文件：

<day = "1"
month = "5"
sunrise ="06:30"
sunset ="21:30"
/>

Answer 1

认为您需要将此 xml 转换为 DateTime，然后使用 TimeZoneInfo 类。

如果丹麦您的当地时间：

DateTime thisTime = DateTime.Now;
bool isDaylight = TimeZoneInfo.Local.IsDaylightSavingTime(thisTime);

否则您需要获得丹麦时区：

DateTime thisTime = DateTime.Now;
// get Denmark Standard Time zone - not sure about that
TimeZoneInfo tst = TimeZoneInfo.FindSystemTimeZoneById("Denmark Standard Time");
bool isDaylight = tst.IsDaylightSavingTime(thisTime);

Answer 2

当我按上述方式编码时 - 对于纽约，我在调试器中发现时间设置正确（包括 DST）

TimeZoneInfo nyTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");

DateTime nyTime = GetLocalDateTime(DateTime.UtcNow, nyTimeZone);

if (nyTimeZone.IsDaylightSavingTime(nyTime))
    nyTime = nyTime.AddHours(1);

public static DateTime GetLocalDateTime(DateTime utcDateTime, TimeZoneInfo timeZone)
    {

        utcDateTime = DateTime.SpecifyKind(utcDateTime, DateTimeKind.Utc);

        DateTime time = TimeZoneInfo.ConvertTime(utcDateTime, timeZone);

        return time;

    }

Answer 3

您可以使用TimeZoneInfo.IsDaylightSavingTime

DateTime theDate = new DateTime(2012, 5, 1); // may 1st
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Central European Standard Time");
bool isCurrentlyDaylightSavings = tzi.IsDaylightSavingTime(theDate);

Answer 4

这是一个通用测试，如果我的数学不正确，很高兴得到纠正。就我而言，我只需要获取时区的 GMT 偏移量，无论它在世界的哪个地方。

  int timezone;

  TimeZoneInfo localZone = TimeZoneInfo.Local;

  DateTime myTime = DateTime.Now;

  bool isDayLight = TimeZoneInfo.Local.IsDaylightSavingTime(myTime);

  if (isDayLight)
            timezone = Math.Abs(localZone.BaseUtcOffset.Hours) + 1;
  else
            timezone = Math.Abs(localZone.BaseUtcOffset.Hours);

  Debug.WriteLine("timezone is " + timezone);

我只是找到了当前时间，如果它在夏令时期间，则将 +1 添加到 GMT 偏移量。

这适用于 Visual Studio Express 2013。

Answer 5

你需要做两件事：

1. 称呼IsAmbiguous
2. 列表项IsDaylightSavingTime。

if (TimeZoneInfo.Local.IsAmbiguousTime(unclearDate) || TimeZoneInfo.Local.IsDaylightSavingTime(unclearDate)) Console.WriteLine("{0} may be daylight saving time in {1}.", unclearDate, TimeZoneInfo.Local.DisplayName);

https://msdn.microsoft.com/en-us/library/bb460642(v=vs.110).aspx

Answer 6

这是我可以在所有时区使用的简短解决方案：

DateTime utcTime = DateTime.Parse("30.10.2018 18:21:34")
DateTime localtime = ConvertUTCToLocalTime(utcTime);


public static DateTime ConvertUTCToLocalTime(DateTime UTCTime)
{
    var localZone = TimeZone.CurrentTimeZone;
    var offset = localZone.GetUtcOffset(UTCTime);
    var localTime = UTCTime.AddHours(offset.Hours);
    return localTime;
}

Answer 7

Based on other codes provided above, I made a complete code to run and make tests. The variable cityTz is receiving an IANA timezone name example. IANA timezone pattern is used in Mac and Linux (Windows uses different timezone style). In 2020, daylight-saving (DST) in New York ends on November 01. If you test the code below, the return will be FALSE, because "theDate" is November 02, the next day after the end of DST. But if you change the line commented and set theDate to November 01 (last DST date in NY), the return will be TRUE.

You can compile this program in Mac or Linux terminal typing:

csc testDST.cs

To run your program:

mono testDST.exe

Complete code:

using System;
using System.Collections.Generic;
using System.Linq;

class Program{
    static void Main(string[] args)
    {
        string cityTz;

        //cityTz = "America/Sao_Paulo";
        cityTz = "America/New_York";

        //DateTime theDate = new DateTime(2020, 11, 1); //returns TRUE
        DateTime theDate = new DateTime(2020, 11, 2); //returns FALSE

        Console.WriteLine("Data: "+theDate);

        TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(cityTz);
        bool isDaylight = tzi.IsDaylightSavingTime(theDate);

        Console.WriteLine("isDaylight this date in "+ cityTz +"?: "+ isDaylight);
    }
}

Answer 8

重要的

myDateTime.IsDaylightSavingTime 确实返回正确的值......但是......它至少精确到一天中的小时，仅通过日期是不够的。

例如，今年 (2019) 3/10/2019 02:00:00 传递为 myDateTime 将返回 false，但 3/10/2019 03:00:00 将返回 true。