Side track: wwvb links 
Chris asks what advantage GPS has over WWVB for my clock project. I don't have a good answer for that (except that having enough controls to select one of 4 mainland US timezones and whether to apply DST is undesirable). However, this did prompt me to do some googling about WWVB. I found some interesting links about generating WWVB signals at home.
Time to finish that languishing clock project! 
A leap second has been announced at the end of June 2012.
Helpful Scripts for CircuitPython & Real Time Clocks (RTCs) 
I have used two different RTCs in the Feather form factor. One has the PCF8523, and the other has the DS3231. The former has an SD card slot while the latter has higher precision including a temperature-compensated crystal oscillator.
Calibrating the DS3231 and PCF8523 RTCs 
… properties to set the best timekeeping possible. Ultimately, because the DS3231 has a TCXO and because…
… it will give the best timekeeping. However, for either device in a constant indoor environment, you…
Minimal Time-Zone Handling for CircuitPython 
For my clock, I want automatic handling of Daylight Saving Time. However, CircuitPython doesn't build in any distinction between local and UTC time, and fitting in the entire Python3 datetime module or an Olson time zone database is simply not going to happen. What can we do that is simple enough to fit, but can represent the reality of timezones where I live?