If you have Locales installed and things won't work check the spelling: for German all the comments suggested "setlocale(LC_TIME, "de_DE.utf8")", but it has to be "setlocale(LC_TIME, "de_DE.UTF-8")"-> UTF-8 instead of utf8.
If you have Locales installed and things won't work check the spelling: for German all the comments suggested "setlocale(LC_TIME, "de_DE.utf8")", but it has to be "setlocale(LC_TIME, "de_DE.UTF-8")"-> UTF-8 instead of utf8.