wcsftime —
convert date and time to a wide-character string
Standard C Library (libc, -lc)
#include <wchar.h>
size_t
  
  wcsftime(wchar_t * restrict wcs,
    size_t maxsize, const wchar_t *
    restrict format, const struct tm * restrict
    timeptr);
The wcsftime() function is equivalent to the
  strftime() function except for the types of its
  arguments and the return value indicating the number of wide characters. Refer
  to strftime(3) for a detailed
  description.
Some early implementations of wcsftime() had a
  format argument with type const char
  * instead of const wchar_t *.
The wcsftime() function conforms to
  ISO/IEC 9899:1999 (“ISO C99”).