Yes a good question. Yet what do we want a clock for ?, timestamp files correctly, remind us of what day it is, tell the time ?. I for one want to trust the picocalc time, and not have to keep checking and correcting it. If untrustworthy then it’s only a rough indicator. My picocalc is certainly within a second 16 hours after first powering on the added DS3231.
In the real world I rely on an accurate watch that also updates itself 2am every morning with a short wave radio signal from an atomic clock. I use it to set all others around the house and in the car and will be watching the picocalc with it of course.
Back to improving my autorun programs ‘daylight saving time’ correction better… Adding the hour to 23:55 caused an error last night 
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