Culture names are <b>not</b> region names (and vice versa)

Back in May of 2004, someone asked the following question in the newsgroups:

I'm programming in ASP.NET. How could I convert my date to UK format ?

Thanks in advance.

To which someone else suggested the following code:

DateTime x=DateTime.Now;
string s=x.ToString(System.Globalization.CultureInfo.CreateSpecificCulture("uk").DateTimeFormat);

To his credit, this code was compiled and ran; in the end he was convinced he had the solution.

However, there are many problems with this code:

• He passed a region to CreateSpecificCulture,  which is expecting a possibly neutral culture (from which it would always return a non-neutral one)
• He passed UK for Great Britain/England/United Kingdom and expected back results that match properties in England, which the ISO standard and .NET uses GB
• He used the CreateSpecificCulture method at all in case where you want to get formatting for a specific location, since its behavior is to pick the first non-neutral culture.¹

So why did the code run, you may skeptically be thinking? Though probably not if you thought about the title of this post!

Well, it has to with the overlap of ISO 639 (the two letter language codes) and ISO 3166 (the two letter region codes). Or in his case, using the wrong abbreviation in the wrong method and having it find some random region that happens to use the abbreviation (in this case the Ukranian neutral locale was being created).

This is kinda unavoidable since

1. there are only so many two-letter combinations
2. language and country names are not always the same
3. there is at least an attempt to make the string choice for each somewhat meaningful
4. the two standards are handled by two different committees that do not work together on assignments

See the following table for a list of the overlaps. The bad overlaps where you will get wrong results are marked in red.

For the full lists of cultures and regions, see the CultureInfo and RegionInfo help topics.

This very non-bug has been reported internally by people wondering why creating a RegionInfo from a neutral (region-less) culture like "AR" was succeeding, as they were not thinking about how when you pass it to a RegionInfo you are not getting "Arabic" you are getting "Argentina".

Of course, this is just a symptom about a larger problem that affects international testing in general, which I will be talking about in a future post. Think of this post as describing the tip of the iceberg. :-)

1 - In this specific case the method would quite literally return the wrong results even if you passed the right language associated with the UK -- en, because the default culture returned from CreateSpecificCulture would be en-US, not en-GB.

This post sponsored by "o", "ο", and "о" (U+006f, U+03bf, and U+043e; a.k.a. LATIN SMALL LETTER O; GREEK SMALL LETTER OMICRON; CYRILLIC SMALL LETTER O).