The user interface culture determines the language in which the administration interface is displayed, as well as other factors like numeric and date formats. UI cultures can be managed and added in Site Manager -> Development -> UI Cultures. The strings that contain the exact text displayed for specific UI cultures are stored in resource files in the CMSResources folder under your web project.
A UI culture can be set for each user in Site Manager -> Administration -> Users -> edit () a user -> General -> Preferred user interface culture.
The default UI culture can be set by adding the following key to the <appSettings> section of your site's web.config file:
<add key="CMSDefaultUICulture" value="en-nz" />
The value of this key must be a valid culture code as in the example above (en-nz represents the English - New Zealand culture).
If you wish to change the default UI culture, you also need to rename the ~\CMSResources\CMS.resx file to CMS.en-us.resx and the CMS.en-nz.resx file to CMS.resx. This is needed because the CMS.resx file is used when the (default) option is selected as a user's Preferred user interface culture.
When the above mentioned key is used and the CMS.resx file contains the en-nz dictionary, the UI culture will be en-nz for users who have their Preferred user interface culture set to (default).
Learn more about configuring a multilingual UI the Configuring multilingual and RTL UI.
Content of Kentico CMS websites (i.e. documents in the content tree) can also be multilingual. To learn about localization of website content, please refer to the Content management -> Multilingual content chapter of this guide.