Month abbreviations show 4 characters instead of 3

Question

I have in code

string dateStr = dateTime.ToString("dd-MMM-yyyy");

On my Windows 11 machine instead of "21-Sep-2021" it generates month with 4 character abbreviation “21-Sept-2021”.

It is generated correctly as 3 characters on the server and other developers machines. https://learn.microsoft.com/en-us/dotnet/api/system.globalization.datetimeformatinfo.abbreviatedmonthnames?view=net-7.0#property-value

I didn’t find where I can change settings. I played with settings as suggested in https://pureinfotech.com/change-time-date-windows-11/ But everything looks ok, Localisation shows “English-Australia”

I’ve confirmed that Australia has 3 characters month abbreviation https://lh.2xlibre.net/locale/en_AU/ and on page https://lh.2xlibre.net/values/abmon/ no localization has 4 character months abbreviations.

I am curious which setting can cause this behaviour?

As a workaround I explicitly specified InvariantCulture

 dateTime.ToString("dd-MMM-yyyy",CultureInfo.InvariantCulture);

Answer 1

That's actually ...... not wrong, although it may not be correct.

From the Australian Government Style Manual, Dates and time

The standard abbreviations for the months are:

• ...
• September – ‘Sept’
• ...

On Windows 11, with NET (Core) 8, using dotnet-repl, this script :

var dateTime=new DateTime(2023,9,21);
var cults=CultureInfo.GetCultures(CultureTypes.AllCultures)
            .Where(ci=>dateTime.ToString("dd-MMM-yyyy",ci)=="21-Sept-2023");
foreach(var cult in cults)
{
    Console.WriteLine("{0} {1}",cult.Name,cult.DisplayName);
}

Produces

en-AU English (Australia)
en-GB English (United Kingdom)

MMM is the specifier for the month abbreviation, not just the first three letters of a month, just as MMMM is the specifier for the full name.

Windows is used by end users, not just developers, so I suspect there were bugs filed that Windows applications don't produce the official abbreviations, even if they aren't the most common ones used in a country.

I've seen similar questions about en-ZA (South Africa) and en-ZW (Zimbabwe). In at least one case both . and , were used as digit separators. One official, one not.