en_US or en-US, which one should you use? [duplicate]

Question

Assume you want to store the locale of user preference in database, which value you will use?

en_US or en-US

They are two standards, but which one you prefer to use as part of your own application?

Updated: Is seems many web sites use dash instead of underscore, e.g.

http://zh.wikipedia.org/zh-tw http://www.google.com.hk/search?hl=zh-TW

Answer 1

I'm pretty sure "-" is the standard. If you see "_" somewhere it's probably something some people came up with to make it a valid identifier.

Personally I'd go with "-", just to be correct.

http://en.wikipedia.org/wiki/IETF_language_tag

https://datatracker.ietf.org/doc/html/rfc5646

Answer 2

If you're working with Java, you might as well use the Java locale format (en_US).

The BCP 47 documents actually do specify the en-US format, and it's just as common if not more common than Java-style locale names. But in practice you'll see the form with the underbar quite a bit. For example, both Java and most POSIX-type platforms use the underbar for their language/region separator.

So you can't go far wrong with either choice. But given that you're writing in Java and probably targeting a Unix platform, en_US is probably the way to go.