admin/environment/php extension/intl
From MoodleDocs
The Internationalization extension (Intl) is a wrapper for the ICU library, a set of C/C++ and Java libraries that provide Unicode and Globalization support for software applications. It enables PHP programmers to perform UCA-conformant collation and date/time/number/currency formatting in their scripts.
To enable this extension add the following line to your php.ini file:
extension=php_intl.dll
And then set the intl.default_locale and intl.error_level directives in your php.ini file.
The intl.error_level directive is optional.
[intl]
intl.default_locale = en_utf8
intl.error_level = E_WARNING
See also
PHP Internationalization Functions
Table of locales lists the locales that you can use.
