If your publication's theme includes a translation for another language, you will need to set the publication language from the site's General settings. For more information on how to translate your theme, please see our i18n documentation.
Set Publication Language
Log in to your publication at http://subdomain.ghost.io/ghost/signin
Go to General from the admin menu
Under Publication Language, click Expand and use the field to set the language/locale to be used on the site. The default is set to English (en).