东部时间应该是 -4 而不是 -5 ？如何在我的应用程序中存储时区偏移量？

Question

I am creating an application that saves the dates on universal time. Later I change the dates according to the timezone that the user specifies.

To save the date I do:

 var dateToSaveOnDatabase = DateTime.Now.ToUniversalTime();

If I go to google I verify the utc date to be:

Now on my app I let the user specify the timezone manually with a number. Lets say the user chooses -5 just like on my computer:**

That means that in my code I have

var userLocalTime = DateTime.Now.ToUniversalTime().AddHours(-5)

If I do that userLocalTime ends up to be equal to 8:00 PM! The eastern time should be 9:00 PM NOT 8:00 PM :/ . If I google what is the eastern time I get:

So my question is why is the eastern time equal to -5 if in reality it is -4 hours away? I am storing the user time zone in a number because the application is used on c# and also on linux. How should I store the timezone in my application?

Answer 1

最好在您的应用程序中存储时区代码，然后进行相应调整。这样你就可以考虑夏令时和其他奇怪的偏移量（不是每个人都有一个小时的偏移量，在少数情况下有些是 30 或 45 分钟）。

在 C# 中使用时区代码从 UTC 转换为用户的时区非常简单，如下所示：

DateTime timeUtc = DateTime.UtcNow;

TimeZoneInfo cstZone = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");

DateTime cstTime = TimeZoneInfo.ConvertTimeFromUtc(timeUtc, cstZone);

东部时间应该是 -4 而不是 -5 ？如何在我的应用程序中存储时区偏移量？

Eastern time should be -4 not -5 ? How can I store the timezone offset on my application?

c#

datetime

timezone

timezone-offset