Why might my local machine be incorrectly formatting international dates?

Question

Here\'s a weird one...

I\'ve just seen a (previously passing) test fail because of extra spaces in a string representation of a date. The test in question has previo

Answer 1

I had the same issue in my Windows 10 machine, got "31. 1. 208". But using:

var format = "d.M.yyyy";

produces: 31.1.2018

it seams to be something with CultureInfo("sk-SK"):

Console.WriteLine(date.ToString("d", new CultureInfo("de-DE")));

produces: 31.01.2018

and

Console.WriteLine(date.ToString("d/M/yyyy", new CultureInfo("de-DE")));

produces: 31.1.2018

(in Windows Control Panel - Region, mine is set as "English - Canada" and short date: "dd/MM/yyyy".

It seems to be defined in the .Net Framework - see the spaces there:

I hope that helps.

Answer 2

In Windows (like many others System), the source for the Locale date/time formats is the Unicode Common Locale Data Repository (CLDR), which provides internationalization and localization support specific for software developers and linguists.
A Short list of meaningful users:

• Microsoft (Windows, Office, Visual Studio etc.)
• Apple (macOS, iOS, watchOS, tvOS, Apple Mobile Device Support and iTunes for Windows;
• Google (Web Search, Chrome, Android, Adwords, Google+, Google Maps, Blogger, Google Analytics)
• IBM (DB2, Lotus, Websphere, Tivoli, Rational, AIX, i/OS, z/OS)
• Amazon

See the Online data explorer of the Localizations: Locale Explorer.

The Short Date format, localized to the sk-SK culture as d. M. yyyy, is the one listed in this archive. It's the same for all OS (Windows 7 to Window 10).

A MS Developer related blog: Locale Builder and Finnish or other locales.

Fiddler or other Online code-runners services are not a source of comparison on this matter.
Locales are different from system to system. Also, these international formats change over time and depend on the updates that a system receives (if it receives these updates at all).

In Windows 7 and Windows 10, the default Short Date format for the sk-SK Culture is d. M. yyyy.
But the DateTime patterns do not match, if the formats list is parsed further.

string format = CultureInfo.CreateSpecificCulture("sk-SK")
                           .DateTimeFormat.GetAllDateTimePatterns()[1]; 

In Windows 7, the second element in the DateTimePatterns list is d.M.yyyy
In Windows 10, the element at the same index is: ffffdd d. MMMM yyyy

A Windows update may change the default pattern for any of the Locales (without explicit notification).
It's understood that applications must provide parsing means for special cases. Or refer to the user Locale settings when formatting, without trying to force a specific pattern for internal uses.
Date/Time formats should be used for presentation only. The Locale and the user settings determine that format. An user of a System may decide to use a different format than the default Locale.

This GitHub repository holds an updated JSON of the CLDR database:
CLDR Date Modern

Also interesting, the ECMAScript reference for API internationalization:
ECMAScript® 2017 Internationalization API Specification

MSDN latest guidelines for Globalization and localization (UWP related):
Globalization and localization
Globalize your date/time/number formats
Use the Multilingual App Toolkit 4.0