99% accurate is pretty vague, but in terms of timekeeping 1% of 24 hours is still almost 15 minutes so being off by a second is couple of orders of magnitude be

99% accurate is pretty vague, but in terms of timekeeping 1% of 24 hours is still almost 15 minutes so being off by a second is couple of orders of magnitude better. Just to give some perspective. NTP definitely should be able to keep the clock correct to sub-second level, but for more accurate local clock something like Open Time Card would do the trick, it has local atomic clock together with GPS receiver to get pretty much reference quality time.