TF_LEN
static char tfbuf[TF_BUFS][TF_LEN]; /* ring buffer */
snprintf(buf, TF_LEN, "%02lluw%01ud%02uh", week, day, hrs);
snprintf(buf, TF_LEN, "%01ud%02uh%02um", day, hrs, min);
snprintf(buf, TF_LEN, "%02u:%02u:%02u", hrs, min, sec);