This is now defined in the Language [lang].xml file in the Language metadata settings. If you are having locale problems such as dates do not appear in your language for example, you might want to check/edit the entries in the locale tag. Note that multiple locale strings can be set and the host will usually accept the first one recognised.
You should publish modules to the "inactive" position and set the Menus to "All", for them to show up on pages where there is no active menu ID. This is a bug/feature of Joomla that causes only menu items in the "All" setting to show up.