Blazor: DateTime.ToString("o") and JsonSerializer.Serialize(DateTime) has a different result in wasm runtime

[anranruye]

Describe the bug

For local DateTime values which are smaller than 1900-12-31 23:59:17, System.Text.Json.JsonSerializer.Serialize(DateTime) has a different result in wasm runtime(+08:05 vs +08:00).

To Reproduce

<button @onclick="Click">Click</button>

@code{
    void Click()
    {
        DateTime dateTime1 = new DateTime(1900, 12, 31, 23, 59, 16, DateTimeKind.Local);
        DateTime dateTime2 = new DateTime(1900, 12, 31, 23, 59, 17, DateTimeKind.Local);
        //Output: "1900-12-31T23:59:16+08:05"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime1));
        Console.WriteLine(dateTime1.ToString("o"));
        //Output: "1900-12-31T23:59:17+08:00"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime2));
        Console.WriteLine(dateTime2.ToString("o"));
    }
}

Exceptions (if any)

Further technical details

• ASP.NET Core version 5.0.0
• Include the output of dotnet --info
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

[ghost]

Tagging subscribers to this area: @eiriktsarpalis, @layomia
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Describe the bug

For local DateTime values which are smaller than 1900-12-31 23:59:17, System.Text.Json.JsonSerializer.Serialize(DateTime) has a different result in wasm runtime(+08:05 vs +08:00).

To Reproduce

<button @onclick="Click">Click</button>

@code{
    void Click()
    {
        DateTime dateTime1 = new DateTime(1900, 12, 31, 23, 59, 16, DateTimeKind.Local);
        DateTime dateTime2 = new DateTime(1900, 12, 31, 23, 59, 17, DateTimeKind.Local);
        //Output: "1900-12-31T23:59:16+08:05"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime1));
        Console.WriteLine(dateTime1.ToString("o"));
        //Output: "1900-12-31T23:59:17+08:00"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime2));
        Console.WriteLine(dateTime2.ToString("o"));
    }
}

Exceptions (if any)

Further technical details

• ASP.NET Core version 5.0.0
• Include the output of dotnet --info
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

Author:	anranruye
Assignees:	-
Labels:	area-System.Text.Json, untriaged
Milestone:	-

[Joe4evr]

This is likely to do with the history of your local timezone. In the late 1800s it wasn't uncommon for certain regions to run both "Railroad time" (which was agreed-upon throughout the country) and "Local time" (which was different between towns/cities, and therefor could be off by a few minutes relative to Railroad time). The key thing to realize here is that at some point in time, the decision has been made to switch every city/town to "Railroad time" so that it'd all be in sync.

Evidently, the timezone data that is consulted for the conversion believes that 1900-12-31 23:59:17 is the moment when that switch happened for your zone.

[anranruye]

@Joe4evr Thank you.

[anranruye]

Now I understand why this happened. However, this makes difference between .Net implements. We still want the same behavior in all .Net implements.

[ghost]

Tagging subscribers to 'arch-wasm': @lewing
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Describe the bug

For local DateTime values which are smaller than 1900-12-31 23:59:17, System.Text.Json.JsonSerializer.Serialize(DateTime) has a different result in wasm runtime(+08:05 vs +08:00).

To Reproduce

<button @onclick="Click">Click</button>

@code{
    void Click()
    {
        DateTime dateTime1 = new DateTime(1900, 12, 31, 23, 59, 16, DateTimeKind.Local);
        DateTime dateTime2 = new DateTime(1900, 12, 31, 23, 59, 17, DateTimeKind.Local);
        //Output: "1900-12-31T23:59:16+08:05"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime1));
        Console.WriteLine(dateTime1.ToString("o"));
        //Output: "1900-12-31T23:59:17+08:00"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime2));
        Console.WriteLine(dateTime2.ToString("o"));
    }
}

Exceptions (if any)

Further technical details

• ASP.NET Core version 5.0.0
• Include the output of dotnet --info
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

Author:	anranruye
Assignees:	-
Labels:	arch-wasm, area-System.Text.Json
Milestone:	7.0.0

[eiriktsarpalis]

System.Text.Json uses the Utf8Formatter class when serializing date values. I would assume there are semantic differences between that implementation and DateTime.ToString("o") in the case of wasm.

[ghost]

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

Issue Details

---

Describe the bug

For local DateTime values which are smaller than 1900-12-31 23:59:17, System.Text.Json.JsonSerializer.Serialize(DateTime) has a different result in wasm runtime(+08:05 vs +08:00).

To Reproduce

<button @onclick="Click">Click</button>

@code{
    void Click()
    {
        DateTime dateTime1 = new DateTime(1900, 12, 31, 23, 59, 16, DateTimeKind.Local);
        DateTime dateTime2 = new DateTime(1900, 12, 31, 23, 59, 17, DateTimeKind.Local);
        //Output: "1900-12-31T23:59:16+08:05"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime1));
        Console.WriteLine(dateTime1.ToString("o"));
        //Output: "1900-12-31T23:59:17+08:00"
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(dateTime2));
        Console.WriteLine(dateTime2.ToString("o"));
    }
}

Exceptions (if any)

Further technical details

• ASP.NET Core version 5.0.0
• Include the output of dotnet --info
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version

Author:	anranruye
Assignees:	-
Labels:	arch-wasm, area-System.Buffers, area-System.Text.Json
Milestone:	7.0.0