Module include PCF8563 IC RTC PCF8563T from NXP, quartz 32.768Kzand LiIon battery socket for 3V battery backup.

The PCF8563 is a CMOS1 Real-Time Clock (RTC) and calendar optimized for low power
consumption. A programmable clock output, interrupt output, and voltage-low detector are
also provided. All addresses and data are transferred serially via a two-line bidirectional
I2C-bus. Maximum bus speed is 400 kbit/s. The register address is incremented
automatically after each written or read data byte

 Provides year, month, day, weekday, hours, minutes, and seconds based on a
32.768 kHz quartz crystal
 Century flag
 Clock operating voltage: 1.0 V to 5.5 V at room temperature
 Low backup current; typical 0.25 A at VDD = 3.0 V and T amb = 25 C
 400 kHz two-wire I 2C-bus interface (at VDD = 1.8 V to 5.5 V)
 Programmable clock output for peripheral devices (32.768 kHz, 1.024 kHz, 32 Hz, and
1 Hz)
 Alarm and timer functions
 Integrated oscillator capacitor
 Internal Power-On Reset (POR)
 I2C-bus slave address: read A3h and write A2h
 Open-drain interrupt pin