DS3231 is equipped with integrated TCXO and crystal, which makes it a cost-effective I2C real time clock with high precision. The device carries a battery input, so if you disconnect the main power supply, it can still maintain accurate timing. The integrated oscillator ensure the long-term accuracy of the device and reduce the number of components. DS3231 provides both commercial and industrial temperature range and supports 16 Lead Small Outline Package (300mil). The module itself can adapt to the system of 3.3V and 5V without level switch and is super convenient! 

Module parameters:

1. Size: 38mm (length) * 22mm (W) * 14mm (height)
2. Weight: 8g
3. Operating voltage :3.3 - 5 .5 V
4. Clock chip: high-precision clock chip DS3231
5. Clock Accuracy :0-40 range, the accuracy 2ppm, the error was about 1 minute
6. Calendar alarm clock with two
7. Programmable square-wave output
8. Real time clock generator seconds, minutes, hours, day, date, month and year timing and provide valid until the year 2100 leap year compensation
9. Chip temperature sensor comes with an accuracy of ± 3
10. Memory chips: AT24C32 (storage capacity 32K)
11. IIC bus interface, the maximum transmission speed of 400KHz (working voltage of 5V)
12. Can be cascaded with other IIC device, 24C32 addresses can be shorted A0/A1/A2 modify default address is 0x57
13. With rechargeable battery CR2032, to ensure the system after power failure, the clock move any natural normal
14. Packing: single anti-static packaging

Wiring instructions ( for Arduino uno r3 for example):
SCL → A5
SDA → A4
VCC → 5V
GND → GND