[time-nuts] RTC DS3231: how well can it be regulated?

[Peter Putnam]

Here's a low-tech look at the DS3231SN and DS3231N, done by eye against 
a clock over a period of three months. No decimal points were abused in 
this procedure.

The goal was to pick the one likely to drift the least over a year at 
room temperature, without changing the aging register.