See www.zabbix.com for the official Zabbix site.
How to/install locale
Install locales in different OS
After implementation of Gettext for Zabbix 2.0 the locales of used languages have to be installed on web server. Some operating systems have installed almost all locales by default (for instance CentOS, FreeBSD).
But if at least one locale is missing a warning message will be shown "You are not able to choose some of the languages, because locales for them are not installed on the web server."
To be able to use an unavailable locale, it has to be installed on a web server where Zabbix frontend is hosted.
Currently installed locales can be checked by the a command locale -a .
In the Debian it's command:
If consider the example above, need to find a record zh_CN.UTF-8 UTF-8, mark it on and press Ok button.
After the locale has been added the Apache daemon has to be restarted to apply these changes:
service apache2 restart