If you have ever tried to write an application that supports multiple languages, I’m sure you will agree that it can be a complicated process. While there are obvious issues, such as translating the text, there are also differing conventions between countries on how things like dates and numbers are formatted, or how letters are sorted. Even just between the different versions of English, there are issues that crop up, such as how being British, I may understand the date 10/07/2013 differently than my American colleagues.
The three areas that the current version one of the spec handles are strings, numbers, and dates. It does this by making a number of existing methods of the String, Number, and Date objects locale aware (that is, you can pass in a locale as an argument), and providing anIntl object that provides further localisation functionality.
Via Jan Hesse