NET6 - Wrong DateTime.ToString() formating when using monoVM and linux-arm

[michaldobrodenka]

Description

DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff") - returns
2021-11-15 14:54:33.3378046 -when app is published with -p:UseMonoRuntime=true.
When using default runtime (without -p:UseMonoRuntime=true) it returns
2021-11-15 15:58:30.675

Reproduction Steps

I was testing minimum possible delay with following program:

using System.Diagnostics;

Stopwatch sw = new Stopwatch();

while(true)
{
    sw.Restart();
    Thread.Sleep(1);
    sw.Stop();
    Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} - Elapsed {sw.ElapsedMilliseconds}");
}

compiled with
dotnet publish -r linux-arm -p:PublishTrimmed=True -p:TrimMode=Link --self-contained true -c Release -f net6.0 -o bin\dotnet\mono -p:UseMonoRuntime=true for mono VM
and
dotnet publish -r linux-arm -p:PublishTrimmed=True -p:TrimMode=Link --self-contained true -c Release -f net6.0 -o bin\dotnet
for default runtime

Expected behavior

fff in DateTime.ToString() should return 1/1000ths of second

Actual behavior

fff in DateTime.ToString() return 1/10 000 000 of second

in screenshot - first with mono, then with dotnet default

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

Tested on 32bit linux-arm on Yocto linux

[dotnet-issue-labeler]

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.

[Clockwork-Muse]

.... the formatting code is unlikely to be in a runtime-dependent section. If you completely clean your build directories, does the issue persist?

[michaldobrodenka]

Yes, I've retested it, deleted all the bin/obj and publish folders.

[michaldobrodenka]

The same program running on Windows PC from VS and deployed to ARM mini PC:

[michaldobrodenka]

Deleted bin, obj & publish folders, dotnet clean, then publish with default runtime, it's ok:

[michaldobrodenka]

Deleted bin, obj & publish folders, dotnet clean, then publish with mono for win-x64, it's ok also:

[michaldobrodenka]

so

• windows x64 mono & dotnet ok
• linux-arm - dotnet ok, mono - bug

[michaldobrodenka]

monoVM linux-x64 tested on WSL - also ok