cppreference.com > Standard C Date & Time > setlocale setlocale Syntax:
      #include <locale.h>
      char *setlocale( int category, const char * locale );
The setlocale() function is used to set and retrieve the current locale. If locale is NULL, the current locale is returned. Otherwise, locale is used to set the locale for the given category. category can have the following values:
Value | Description
--- | ---
LC_ALL | All of the locale
LC_TIME | Date and time formatting
LC_NUMERIC | Number formatting
LC_COLLATE | String collation and regular expression matching
LC_CTYPE | Regular expression matching, conversion, case-sensitive comparison, wide character functions, and character classification.
LC_MONETARY | For monetary formatting
LC_MESSAGES | For natural language messages
Related topics: (Standard C String and Character) strcoll