A DS1307 real-time clock module paired with a small OLED screen turns Arduino into a standalone digital clock that keeps accurate time even when it's…
A look at the DS1307's details: its backup battery system, the SQW square-wave output, and its built-in EEPROM memory.
Understand DS3231 accuracy, temperature compensation, backup power, and the difference between the RTC IC and optional EEPROM on breakout boards.
A guide to wiring an RTC module over I2C to keep accurate time and date even after power is disconnected.