DS1307 I2C real-time clock chip (RTC)
24C32 32K I2C EEPROM memory
Socket for LIR2032 rechargeable lithium battery (not included) to keep RTC clock running while the microprocessor is off.
Fully charged battery should support module for a year.
Breakout for DS1307 clock pin, to provide the clock signal for the microcontroller.
Compact design, 27mm * 28mm * 8.4mm
Can be cascaded to other I2C devices.