You're confusing language and locale and that's going to be equally confusing to your users. I read web content in several languages and expect date formats in

You're confusing language and locale and that's going to be equally confusing to your users. I read web content in several languages and expect date formats in ALL applications my application to follow my OS locale which is Finnish. My Windows operating system is in English, yet my locale is Finnish, so that the date format is Finnish. This is the standard way of using locales. Why would web sites be any different?