c# - 将 UTC 日期时间转换为另一个时区

Question

我有一个来自数据库记录的 UTC DateTime 值。我还有一个用户指定的时区（TimeZoneInfo 的一个实例）。如何将该 UTC DateTime 转换为用户的本地时区？另外，如何确定用户指定的时区当前是否正在遵守 DST？我正在使用.NET 3.5。

谢谢，马克

Answer 1

最好的方法就是简单地使用TimeZoneInfo.ConvertTimeFromUtc.

// you said you had these already
DateTime utc = new DateTime(2014, 6, 4, 12, 34, 0);
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");

// it's a simple one-liner
DateTime pacific = TimeZoneInfo.ConvertTimeFromUtc(utc, tzi);

唯一的问题是传入的DateTime值可能没有DateTimeKind.Local那种类型。它必须是Utc或Unspecified。

Answer 2

如果要将 DateTimeOffset 转换为另一个 DateTimeOffset，可以在 TimeZoneInfo 中使用专用函数：

DateTimeOffset newTime = TimeZoneInfo.ConvertTime(
    DateTimeOffset.UtcNow, 
    TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")
);

Answer 3

看看DateTimeOffset结构：

// user-specified time zone
TimeZoneInfo southPole =
    TimeZoneInfo.FindSystemTimeZoneById("Antarctica/South Pole Standard Time");

// an UTC DateTime
DateTime utcTime = new DateTime(2007, 07, 12, 06, 32, 00, DateTimeKind.Utc);

// DateTime with offset
DateTimeOffset dateAndOffset =
    new DateTimeOffset(utcTime, southPole.GetUtcOffset(utcTime));

Console.WriteLine(dateAndOffset);

对于 DST，请参阅TimeZoneInfo.IsDaylightSavingTime方法。

bool isDst = southpole.IsDaylightSavingTime(DateTime.UtcNow);

Answer 4

南极洲的答案仅适用于与 UTC 匹配的时区。我对这个DateTimeOffset功能感到非常痛苦，经过数小时的反复试验，我设法产生了一个适用于所有时区的实用转换扩展功能。

static public class DateTimeFunctions
{
    static public DateTimeOffset ConvertUtcTimeToTimeZone(this DateTime dateTime, string toTimeZoneDesc)
    {
        if (dateTime.Kind != DateTimeKind.Utc) throw new Exception("dateTime needs to have Kind property set to Utc");
        var toUtcOffset = TimeZoneInfo.FindSystemTimeZoneById(toTimeZoneDesc).GetUtcOffset(dateTime);
        var convertedTime = DateTime.SpecifyKind(dateTime.Add(toUtcOffset), DateTimeKind.Unspecified);
        return new DateTimeOffset(convertedTime, toUtcOffset);
    }
}

例子：

var currentTimeInPacificTime = DateTime.UtcNow.ConvertUtcTimeToTimeZone("Pacific Standard Time");

Answer 5

       //  TO get Currrent Time in current Time Zone of your System

        var dt = DateTime.Now;

        Console.WriteLine(dt);

        // Display Time Zone of your System

        Console.WriteLine(TimeZoneInfo.Local);

        // Convert Current Date Time to UTC Date Time

        var utc = TimeZoneInfo.ConvertTimeToUtc(dt, TimeZoneInfo.Local);

        Console.WriteLine(utc);

        // Convert UTC Time to Current Time Zone

        DateTime pacific = TimeZoneInfo.ConvertTimeFromUtc(utc, TimeZoneInfo.Local);

        Console.WriteLine(pacific);

        Console.ReadLine();

Answer 6

这是另一个问题：如果您在 Linux 服务器上运行代码，则需要使用 Linux 系统作为时区名称。例如，“Central Standard Time”将是“America/Chicago”。tz 列表在这里： https ://en.wikipedia.org/wiki/List_of_tz_database_time_zones

这是 isWindows 开关的示例：

public static class DateTimeHelper
{
    public static string ConvertUtcToCst(this string dateTimeString)
    {
        if (string.IsNullOrWhiteSpace(dateTimeString))
        {
            return string.Empty;
        }

        if (DateTime.TryParse(dateTimeString, out DateTime outputDateTime))
        {
            try
            {
                var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
                TimeZoneInfo cstZone = null;
                if (isWindows)
                {
                    cstZone = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");
                }
                else
                {
                    cstZone = TimeZoneInfo.FindSystemTimeZoneById("America/Chicago");
                }

                var cstDateTime = TimeZoneInfo.ConvertTimeFromUtc(outputDateTime, cstZone);
                return cstDateTime.ToString();
            }
            catch (TimeZoneNotFoundException)
            {
                return "The registry does not define the Central Standard Time zone.";
            }
            catch (InvalidTimeZoneException)
            {
                return "Registry data on the Central Standard Time zone has been corrupted.";
            }
            catch (Exception ex)
            {
                return $"Error :: {ex.Message} :: {ex.ToString()}";
            }
        }

        return string.Empty;
    }
}