This module is a Real-Time Clock (RTC) with a super capacitor used for unpowered time retention. The I2C interfaced DS3231 hss an RTC/TCXO/Crystal integrated in the chip.

The module run on 3.3V or 5V.

Pin Out:

Pin 2 = SDA
Pin 3 = SCL
Pin 4 = N/C
Pin 5 = GND