Language Configuration
In normal cases, ownCloud will automatically detect the language of the Web UI. If this does not work as expected, or you want to make sure that ownCloud always starts with a given language, you can use the default_language configuration parameter.
This parameter can be set in config/config.php
Parameters
'default_language' => 'en',Keep in mind that this will not affect the language preferences of users, which can be configured under once they have logged in.
More supported languages can be found in directory <ownCloud_root>/settings/l10n. List all files with ls *.js. The language code to be used is the filename without extension.
Example:
en_GB.js --> en_GB
Refer to Wikipedia for a match of language code to country.