ATmega328p clock based on DS3231 clock calendar module.
Simple clock with calendar based on atmega328p MCU and DS3231 real time clock module.
Features:
clock
calendar up to year 2100
room temperature sensor
128x64 graphical LCD screen
automatic LCD brightness control
power saving modes
backup Li-Ion battery
encoder as user input
hold for 5 seconds encoder button to start date time setup
Original schematics and some pictures can be found here