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.
Build an educational medication reminder with Arduino, DS3231, an LCD and a buzzer, including safe wiring, working code, and a test checklist.