Inconsistencies with DateTime string formatting #2408

Description

There are several inconsistencies with DateTime and different DateTimeKinds when formatting as string:

%A is different for Kind=Local and Kind=Utc

%A for a local DateTime formats the DateTime completely different from UTC DateTime

Repro code

let local = DateTime(2020, 02, 20, 20, 20, 20, DateTimeKind.Local)
let utc = DateTime(2020, 02, 20, 20, 20, 20, DateTimeKind.Utc)

printfn "local = %A" local
printfn "utc   = %A" utc

(repl)

Expected and actual results

Actual output:

local = 2/20/2020, 8:20:20 PM
utc = Thu, 20 Feb 2020 20:20:20 GMT

Expected output:
Both should be in similar format -- especially same culture format.

In .NET:

local = 2020-02-20 20:20:20
utc = 2020-02-20 20:20:20

(Tough I think it's reasonable to include some indication of timezone, like it's done in Fable with utc (even though utc is technically not a timezone... GMT <> UTC...))

%A and ToString() are different

Repro code

let dt = DateTime(2020, 02, 20, 20, 20, 20)
printfn "dt            = %A" dt
printfn "dt.ToString() = %s" (dt.ToString())

(repl)

Expected and actual results

Actual output:

dt = 2/20/2020, 8:20:20 PM
dt.ToString() = Thu Feb 20 2020 20:20:20 GMT+0100 (Central European Standard Time)

Expected output:
Both should be in same format, and probably not the overcomplex one of ToString without any formatters.
And both should use same culture formatting.

In .NET:

dt = 2020-02-20 20:20:20
dt.ToString() = 2020-02-20 20:20:20

Using a Utc DateTime results in more similar representations:

let dt = DateTime(2020, 02, 20, 20, 20, 20, DateTimeKind.Utc)
printfn "dt            = %A" dt
printfn "dt.ToString() = %s" (dt.ToString())

(repl)

Output:

dt = Thu, 20 Feb 2020 20:20:20 GMT
dt.ToString() = Thu Feb 20 2020 21:20:20 GMT+0100 (Central European Standard Time)

But oddly still not the same: Thu, 20 Feb vs Thu Feb 20 ...

Related information

• Versions:
  • Fable: 3.1.5
  • Repl: 3.1.5
• Local System Settings:
  • TimeZone: CET (Central European Time -- UTC + 1)
  • date/time formatting: yyyy-MM-dd HH:mm:ss (2020-02-20 20:20:20)