VMS Help CC, Run-time functions, wcsftime  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  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.

  Syntax:

     #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)