It's a DS1307- Real Time Clock Module. It is RTC based module which Consumes less than 500nA in battery backup mode with oscillator running. The module comes fully assembled and pre-programmed with the current time.
Features 
- DS1307 based RTC Module.
 
- 1Hz output pin.
 
- Consumes less than 500nA in battery backup mode with oscillator running
 
- Underwriters Laboratory (UL) recognized
 
- Real-time clock (RTC) counts seconds, minutes, hours, date of the month, month, day of the week, and year with leap-year compensation valid up to 2100
 
- 56-byte non-volatile RAM for data storage
 
- 56 Bytes of Non-volatile memory available to the user.
 
- The DS1307 is accessed via the I2C protocol.
 
- The module comes fully assembled and pre-programmed with the current time.