fmt_timeframe(time_t t)
{
	char		*buf;
	static char	 tfbuf[TF_BUFS][TF_LEN];	/* ring buffer */
	static int	 idx = 0;
	unsigned int	 sec, min, hrs, day;
	unsigned long long	week;

	buf = tfbuf[idx++];
	if (idx == TF_BUFS)
		idx = 0;

	week = t;

	sec = week % 60;
	week /= 60;
	min = week % 60;
	week /= 60;
	hrs = week % 24;
	week /= 24;
	day = week % 7;
	week /= 7;

	if (week > 0)
		snprintf(buf, TF_LEN, "%02lluw%01ud%02uh", week, day, hrs);
	else if (day > 0)
		snprintf(buf, TF_LEN, "%01ud%02uh%02um", day, hrs, min);
	else
		snprintf(buf, TF_LEN, "%02u:%02u:%02u", hrs, min, sec);

	return (buf);
}