os/setlocale

    cfunction
    src/core/os.c on line 2012, column 1

    (os/setlocale &opt locale category)

    Set the system locale, which affects how dates and numbers are 
    formatted. Passing nil to locale will return the current locale. 
    Category can be one of:

    * :all (default)
    * :collate
    * :ctype
    * :monetary
    * :numeric
    * :time

    Returns the new locale if set successfully, otherwise nil. Note 
    that this will affect other functions such as `os/strftime` and 
    even `printf`.