Here's some data that may be interesting concerning the accuracy of this clock thus far.
Clock with NIST, with the following results:
Clock Watch NIST Watch 8:00:00 8:00:00.00 8:10:00 8:09:59.38 8:01:00 8:00:59.89 8:11:00 8:10:59.42 8:02:00 8:01:59.99 8:12:00 8:11:59.39 8:03:00 8:03:00:00 8:13:00 8:12:59.24 8:04:00 8:03:59.90 8:14:00 8:13:59.39
Average of five measurements: 8:00:00 7:59:59.956 8:00:00 7:59:59.364
So the clock is now ahead of NIST by 0.956 - 0.364 = 0.592 seconds.
We started the clock speed test on 02/17/22 so now the results so far are:
03/04/22 02/17/22
Clock Time 07:59.59.956 12:00:00.176
NIST Time 07:59:59.364 11:59:59.774
Difference 0.592 second 0.402 second
So the clock is now ahead of NIST by 0.592 seconds and it was originally ahead of NIST by 0.402 seconds, so it has actually gained only 0.592 - 0.402 = 0.190 seconds in 03/04/22 - 02/17/22 = 14.83333 days. So the clock is running fast by 0.190/14.8333 = 0.0128 sec/day = 12.8 ms/day = 0.39 sec/month = 4.68 sec/year.
Your accuracy may vary due to climate conditions in your location, and time of year. We expect to do another calibration in a few months.
Our thermostat keeps our temperature very close to 74 degrees. So that probably helps the stability quite a bit. We did make the measurements visually, but for every measurement we took five and averaged to get a little better fractions of a second. We used a stopwatch for both the clock measurements and the measurements of the NIST time standard signals at https://time.gov