buflen = 64;
  Newx(buf, buflen, char);
  len = strftime(buf, buflen, fmt, &mytm);
  /*
  ** The following is needed to handle to the situation where
  ** tmpbuf overflows.  Basically we want to allocate a buffer
  ** and try repeatedly.  The reason why it is so complicated
  ** is that getting a return value of 0 from strftime can indicate
  ** one of the following:
  ** 1. buffer overflowed,
  ** 2. illegal conversion specifier, or
  ** 3. the format string specifies nothing to be returned(not
  **	  an error).  This could be because format is an empty string
  **    or it specifies %p that yields an empty string in some locale.
  ** If there is a better way to make it portable, go ahead by
  ** all means.
  */
  if ((len > 0 && len < buflen) || (len == 0 && *fmt == '\0'))
    return buf;
  else {
    /* Possibly buf overflowed - try again with a bigger buf */
    const int fmtlen = strlen(fmt);
    int bufsize = fmtlen + buflen;

    Newx(buf, bufsize, char);
    while (buf) {
      buflen = strftime(buf, bufsize, fmt, &mytm);
      if (buflen > 0 && buflen < bufsize)
	break;
      /* heuristic to prevent out-of-memory errors */
      if (bufsize > 100*fmtlen) {
	Safefree(buf);
	buf = NULL;
	break;
      }
      bufsize *= 2;
      Renew(buf, bufsize, char);
    }
    return buf;
  }
#