We know Raspberry Pi is a single board computer, aiming to promote computer engineering and programming. It is very compact and is a fully functioning computer motherboard. Yet, it lack of Real Time Clock. This RTC module is specifically designed for Raspberry Pi. It communicate with Raspberry Pi through I2C bus. There is a DS3231 and a small button battery on the board to keep the real time for a long time after the Raspberry Pi has it's power DS3231 has better performance compared to DS1307, lower power consumption too. DS3231 comes with temperature compensated crystal, so the time counting is more accurate over time and over temperature. Best of all, this module is 3.3V and 5V compatible, it can be used with Arduino too, besides Raspberry Pi Can also be used w Arduino. DS3231 RTC IC Self-adjust 3.3V and 5V. Provide battery backup for continuous timing, Low-power consumption. Complete clock functions include seconds, minutes, hours, day, date, month, and year timing, and provide valid to 2100. It has Two calendar alarms, 1Hz, and 12.768kHz output. Reset output and input buttons Debounced High-speed (400KHz) I2C serial bus. Many RTC modules are meant to operate at 5V. Unfortunately, the Raspberry Pi operates at 3.3V, that is where this handy module comes into play, it operates at 3.3V perfect for adding an RTC to your Raspberry Pi.