Uses date and time information stored in a tm structure to create
    a wide-character output string. The format of the output string
    is controlled by a format string.

    Format

      #include  <wchar.h>

      size_t wcsftime  (wchar_t *wcs, size_t maxsize, const char
                       *format, const struct tm *timeptr); (XPG4)

      size_t wcsftime  (wchar_t *wcs, size_t maxsize, const wchar_t
                       *format, const struct tm *timeptr); (ISO C)