It is a real-time clock (RTC) module with DS1307 chip. It works with I2C communication protocol and connects to A4 (SDA) and A5 (SCL) pins of Arduino. Thanks to the CR2032 battery on it, it continues to maintain the time and date information even if the Arduino is de-energized. It provides uninterrupted time tracking for projects by keeping seconds, minutes, hours, days, months and years. It is widely used in projects such as data storage, alarm systems, automatic irrigation and timers.