`DateTime.Now` on Linux has wrong timezone

[ivan7wl]

Description

When use DateTime.Now on my Linux machine, dotnet assume the timezone is UTC.

Reproduction Steps

Using Ubuntu 20.04:

$ timedatectl status
               Local time: 五 2021-10-15 21:07:22 CST
           Universal time: 五 2021-10-15 13:07:22 UTC
                 RTC time: 五 2021-10-15 13:07:22    
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: yes                       
              NTP service: active                    
          RTC in local TZ: no

However the code:

DateTime localNow = DateTime.Now;
DateTime utcNow = DateTime.UtcNow;
Console.WriteLine($"localNow: {localNow}, {localNow.Kind}, utcNow: {utcNow}, {utcNow.Kind}");
Console.WriteLine($"TimeZoneInfo.Local: {TimeZoneInfo.Local}");

Produces output:

localNow: 10/15/2021 13:07:25, Local, utcNow: 10/15/2021 13:07:25, Utc
TimeZoneInfo.Local: (UTC) Coordinated Universal Time

Expected behavior

DateTime.Now has the proper local time.

Actual behavior

DateTime.Now always equal to UTC time, no matter what the system timezone is.

Regression?

No response

Known Workarounds

No response

Configuration

Using dotnet sdk 6.0.100-rc.1.21463.6 on Linux (Ubuntu 20.04).

$ dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100-rc.1.21463.6
 Commit:    e627d556a1

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  20.04
 OS Platform: Linux
 RID:         ubuntu.20.04-x64
 Base Path:   /opt/dotnet/sdk/6.0.100-rc.1.21463.6/

Host (useful for support):
  Version: 6.0.0-rc.1.21451.13
  Commit:  d7619cd4b1

.NET SDKs installed:
  5.0.401 [/opt/dotnet/sdk]
  6.0.100-rc.1.21463.6 [/opt/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.10 [/opt/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-rc.1.21452.15 [/opt/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.10 [/opt/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-rc.1.21451.13 [/opt/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

Other information

UPDATE:
I found this issue may relate to RTC settings:

$ timedatectl set-local-rtc 1 --adjust-system-clock
$ sudo reboot
...
$ timedatectl status
               Local time: 五 2021-10-15 23:25:15 CST
           Universal time: 五 2021-10-15 15:25:15 UTC
                 RTC time: 五 2021-10-15 15:25:16    
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: yes                       
              NTP service: active                    
          RTC in local TZ: yes                       

Warning: The system is configured to read the RTC time in the local time zone.
         This mode cannot be fully supported. It will create various problems
         with time zone changes and daylight saving time adjustments. The RTC
         time is never updated, it relies on external facilities to maintain it.
         If at all possible, use RTC in UTC by calling
         'timedatectl set-local-rtc 0'.
$ dotnet run
localNow: 10/15/2021 23:25:25, Local, utcNow: 10/15/2021 15:25:25, Utc
TimeZoneInfo.Local: (UTC+08:00) CST

But this is weird, when I use timedatectl set-local-rtc 0 --adjust-system-clock to set it back, this issue cannot be reproduced anymore.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[danmoseley]

@tarekgh

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

When use DateTime.Now on my Linux machine, dotnet assume the timezone is UTC.

Reproduction Steps

Using Ubuntu 20.04:

$ timedatectl status
               Local time: 五 2021-10-15 21:07:22 CST
           Universal time: 五 2021-10-15 13:07:22 UTC
                 RTC time: 五 2021-10-15 13:07:22    
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: yes                       
              NTP service: active                    
          RTC in local TZ: no

However the code:

DateTime localNow = DateTime.Now;
DateTime utcNow = DateTime.UtcNow;
Console.WriteLine($"localNow: {localNow}, {localNow.Kind}, utcNow: {utcNow}, {utcNow.Kind}");
Console.WriteLine($"TimeZoneInfo.Local: {TimeZoneInfo.Local}");

Produces output:

localNow: 10/15/2021 13:07:25, Local, utcNow: 10/15/2021 13:07:25, Utc
TimeZoneInfo.Local: (UTC) Coordinated Universal Time

Expected behavior

DateTime.Now has the proper local time.

Actual behavior

DateTime.Now always equal to UTC time, no matter what the system timezone is.

Regression?

No response

Known Workarounds

No response

Configuration

Using dotnet sdk 6.0.100-rc.1.21463.6 on Linux (Ubuntu 20.04).

$ dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100-rc.1.21463.6
 Commit:    e627d556a1

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  20.04
 OS Platform: Linux
 RID:         ubuntu.20.04-x64
 Base Path:   /opt/dotnet/sdk/6.0.100-rc.1.21463.6/

Host (useful for support):
  Version: 6.0.0-rc.1.21451.13
  Commit:  d7619cd4b1

.NET SDKs installed:
  5.0.401 [/opt/dotnet/sdk]
  6.0.100-rc.1.21463.6 [/opt/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.10 [/opt/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-rc.1.21452.15 [/opt/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.10 [/opt/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-rc.1.21451.13 [/opt/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

Other information

No response

Author:	ivan7wl
Assignees:	-
Labels:	area-System.Runtime, untriaged
Milestone:	-

[hez2010]

I cannot reproduce it with .NET 6 rc2, could you try again with rc2?

[ivan7wl]

I cannot reproduce it with .NET 6 rc2, could you try again with rc2?

Hi @hez2010, thanks for the reply. I also tried on dotnet 5.0.401 and 6.0.100-rc.2.21505.57, still has this issue.

[hez2010]

@ivan7wl
Can you execute following commands and see what are being printed in your environment?

echo $TZ
echo $TZDIR
ls -l /etc/localtime
date

Since .NET reads time zone information from /etc/localtime and $TZDIR/$TZ, this might be an issue related to your environment.

[ivan7wl]

I cannot reproduce it with .NET 6 rc2, could you try again with rc2?

Hi, please checkout the UPDATE in Other Information.

[ivan7wl]

@ivan7wl Can you execute following commands and see what are being printed in your environment?

echo $TZ
echo $TZDIR
ls -l /etc/localtime
date

Hi @hez2010 , I cannot reproduce this issue anymore, after I run the timedatectl command.
But I've check $TZ and etc/localtime when I first found this issue, $TZ is empty, and etc/localtime is linked to /usr/share/zoneinfo/Asia/Shanghai.

[ivan7wl]

I don't know why but things are get more and more complicated, I can now reproduce this on 6.0.100-rc.2.21505.57, but cannot reproduce on 5.0.401.

test_project_50$ dotnet run
localNow: 10/15/2021 23:59:19, Local, utcNow: 10/15/2021 15:59:19, Utc
TimeZoneInfo.Local: (UTC+08:00) CST
test_project_50$ cd ../test_project_60/
test_project_60$ dotnet run
localNow: 10/15/2021 15:59:28, Local, utcNow: 10/15/2021 15:59:28, Utc
TimeZoneInfo.Local: (UTC) Coordinated Universal Time

[tarekgh]

@ivan7wl

Could you please try to create a simple Console application from scratch using dotnet new Console and paste the following code in the main and send the result?

    Console.WriteLine($"{RuntimeInformation.OSDescription}");
    Console.WriteLine($"{RuntimeInformation.FrameworkDescription}");
    Console.WriteLine($".... Invariant:              {typeof(object).Assembly.GetType("System.Globalization.GlobalizationMode").GetProperty("Invariant", BindingFlags.Static | BindingFlags.NonPublic).GetValue(null)} ....");
    Console.WriteLine($"{TimeZoneInfo.Local.Id}");

please run this console app against .NET 6.0 and 5.0.

if you still see the issue, please share to us the file /usr/share/zoneinfo/Asia/Shanghai also try to change the TZ setting on that machine to any other zone just for testing if the issue is with Shanghai TZ only or it is generic issue on the whole machine? I'll try to look offline too.