This tiny RTC module is based on the clock chip DS1307 which supports the I2C protocol. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The RTC module use the I2C bus to communicate with Arduino.
DS1307 I2C real time clock chip (RTC)24C32 32K I2C EEPROM memoryLeads to the DS1307 clock pin provides a clock signal for the microcontrollerOther I2C devices can be cascaded.
**Comes without battery. Get your battery HERE
Reference
Please refer to sample code and wiring HERE