system/config/locale.php
language
Default language locale name(s). First item must be a valid i18n directory name, subsequent items are alternative locales for OS's that don't support the first (e.g. Windows). The first valid locale in the array will be used.
Default value: array('en_US', 'English_United States');
timezone
Locale timezone. Defaults to use the server timezone.
Default value: '';