This project was about 5 years old. It had an old Mega8 avr on it ... pre arduino. but I lost the code in a hard drive crash and placed it in a drawer. When I saw Ahmed Mohamed's story I though of all the electronics projects I built in high school. Clocks, Blinking neon lights, Radios, and parts of a pong game. So I dug it out and arduinoized it.(sorry, but time is precious). the displays are vintage HP and contain latches, decoders and LED s in one neat package. there are no segments but groups of dots. It makes for a very distictive look.
Time is kept by the DS3231 board which should hold better than 2 mins a year. The arduino nano reads the DS3231 and updates the displays by writing 4 bits to the display digit and strobing it's latch. Repeat for each digit. The displays are power hungry , about .5W each.