You can build a digital clock with a large 7-segment display, a Feather RP2040, and CircuitPython -- no internet required! For time keeping, this build uses the DS3231 Real Time Clock module for precise and accurate timing. 

Full Tutorial
https://learn.adafruit.com/digital-clock-with-circuitpython/ 

Code on GitHub
https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/Digital_Clock_with_CircuitPython/code.py 

1.2in LED 7-Segment Display 
https://www.adafruit.com/product/1271 

Feather RP2040
https://www.adafruit.com/product/4884 

DS3231 RTC STEMMA QT
https://www.adafruit.com/product/5188 

Rotary Encoder STEMMA QT
https://www.adafruit.com/product/4991