DT_BUF_LEN
char buf[DT_BUF_LEN];
char datetime[DT_BUF_LEN];
(void) strftime(datetime, DT_BUF_LEN, datetime_fmt, tm);
char datetime[DT_BUF_LEN];
(void) strftime(datetime, DT_BUF_LEN, datetime_fmt, tm);
char datetime[DT_BUF_LEN];
(void) strftime(datetime, DT_BUF_LEN, datetime_fmt, tm);
CTASSERT(DT_BUF_LEN >= NN_NUMBUF_SZ);