>I just used the basic app, I did not change anything there.

hm, if so then it is depends on your pc locale settings i guess that `intl` is using, as for me the default basic app give [this](https://github.com/yiisoft/yii2/issues/2299#issuecomment-34393370) and it's correct.

>How do I find out the locale used by Yii?

by default Yii language is en-US afaik, not sure. Locale and language are now the [same](https://github.com/yiisoft/yii2/blob/master/framework/i18n/Formatter.php#L40) since `intl` is used.