As promised, I am returning with the sketch (download from here).
Justin and Wyolum Co. also promised (wink, wink) that the next revision of I2SD will have the needed digital pins accessible through headers.
This "mixed breed wise clock" is using the I2SD (with on-board RTC and SD card), the display (and idea) from Book Clock, and code borrowed and adapted from Wise Clock 2.
Missing are the user buttons and a tilt switch, which may be connected to the free A0/D15 - A3/D18 pins available on the header of the I2SD board. (Note: The buttons and the tilt switch should be also supported in software as well, code which can be copied from the existing Wise Clock 2 and Book Clock sketches.)
How does an ADC work?
2 hours ago