TimeZoneInfo in .NET Core when hosting on unix (nginx)

For example, when I try to do the following.

TimeZoneInfo.FindSystemTimeZoneById("Central European Standard Time")

I get the error, that the TimeZone is not available on the local computer. When I run this locally it works, but there I run it on windows. When deployed it runs on a Unix machine in Nginx. I can see that FindSystemTimeZoneById is looking in the wrong folder when it comes to Unix. Is there any way to make this work?

.Net Core using system timezone. Unfortunately Windows and Linux have different timezone system. Now you have two ways:

• Use other (and universal) impementation of timezone like Noda time
• Translate between Windows and IANA time zones, e.g. using the TimeZoneConverter micro-library.

Working of off the previous answer, we can avoid the expensive try/catch by checking which OS we're running on:

using System;
using System.Runtime.InteropServices;

TimeZoneInfo easternStandardTime;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
  easternStandardTime = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
}
if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
{
  easternStandardTime = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");
}
if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
  easternStandardTime = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");
}

Can you please try this?

   TimeZoneInfo easternZone;
        try
        {
            easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
        }
        catch (TimeZoneNotFoundException)
        {
            easternZone = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");
        }

You can review the list of IANA time zones here https://en.wikipedia.org/wiki/List_of_tz_database_time_zones

If you want to try a Windows time zone and then fallback on a IANA one if the Windows one doesn't exist:

var tzi  = TimeZoneInfo.GetSystemTimeZones().Any(x => x.Id == "Eastern Standard Time") ? 
    TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time") : 
    TimeZoneInfo.FindSystemTimeZoneById("America/New_York");

I was able to support this use-case in my development docker image by doing the following:

cp /usr/share/zoneinfo/America/Los_Angeles "/usr/share/zoneinfo/Pacific Standard Time"

Obviously, I don't think that would be a good idea for production deployments. But it might help in some scenarios.

Starting with .NET 6, it is finally possible to work with time zones in a cross-platform manner.

The TimeZoneInfo.FindSystemTimeZoneById(string) method automatically accepts either Windows or IANA time zones on either platform and convert them if needed.

// Both of these will now work on any supported OS where ICU and time zone data are available.
TimeZoneInfo tzi1 = TimeZoneInfo.FindSystemTimeZoneById("AUS Eastern Standard Time");
TimeZoneInfo tzi2 = TimeZoneInfo.FindSystemTimeZoneById("Australia/Sydney");

Note that, as specified on the link, the .NET Core Alpine Linux-based Docker images do not have the necessary tzdata installed by default, so it must be installed in your Dockerfile for this to work correctly.

Quick and dirty solution: serialize your TimeZoneInfo with ToSerializedString in a dummy app on Windows, save the output, then deserialize with FromSerializedString where you need it.

On Windows:

Console.WriteLine(TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"));

Output:

Eastern Standard Time;-300;(UTC-05:00) Eastern Time (US & Canada);Eastern Standard Time;Eastern Daylight Time;[01:01:0001;12:31:2006;60;[0;02:00:00;4;1;0;];[0;02:00:00;10;5;0;];][01:01:2007;12:31:9999;60;[0;02:00:00;3;2;0;];[0;02:00:00;11;1;0;];];

Then:

// TimeZoneInfo is immutable
public static readonly TimeZoneInfo EST = TimeZoneInfo.FromSerializedString(
            "Eastern Standard Time;-300;(UTC-05:00) Eastern Time (US & Canada);Eastern Standard Time;Eastern Daylight Time;[01:01:0001;12:31:2006;60;[0;02:00:00;4;1;0;];[0;02:00:00;10;5;0;];][01:01:2007;12:31:9999;60;[0;02:00:00;3;2;0;];[0;02:00:00;11;1;0;];];");