Package Includes: 1 piece x DS1307 RTC Module - Real Time Clock Module
 
Real Time Clock (RTC) is used to track the current time and date. It is generally used in computers, laptops, mobiles, embedded system applications devices etc.
In many embedded system, we need to put time stamp while logging data i.e. sensor values, GPS coordinates etc. For getting timestamp, we need to use RTC (Real Time Clock).
Some microcontrollers like LPC2148, LPC1768 etc., have on-chip RTC. But in other microcontrollers like PIC, ATmega16/32, they do not have on-chip RTC. So, we should use external RTC chip
There are different types of ICs used for RTC like DS1307, DS12C887 etc.
 
Features and Specifications of DS1307:
The RTC module is based on DS1307 high precision real time clock module;
Through I2C interface to communicate with singlechip, Real Time Clock,Timer,Alarm,Calendar can read year, month, day, week, time, minute, second; Can read until 2100 year;
Control interface is I2C; Recommended power: DC 5V; The address of the module is 0x68; Control interface level is 5V or 3.3V.
56-byte, battery-backed, nonvolatile (NV) RAM for data storage
Two-wire serial interface
Programmable squarewave output signal
Automatic power-fail detect and switch  circuitry
Consumes less than 500nA in battery backup  mode with oscillator running
 
Connections:
5V is used to power to the RTC chip when you want to query it for the time. If there is no 5V signal, the chip goes to sleep using the coin cell for backup.
Connect GND to common power/data ground
Connect the SCL pin to the I2C clock SCL pin on your Arduino. On an UNO & '328 based Arduino, this is also known as A5, on a Mega it is also known as digital 21 and on a Leonardo/Micro, digital 3
Connect the SDA pin to the I2C data SDA pin on your Arduino. On an UNO & '328 based Arduino, this is also known as A4, on a Mega it is also known as digital 20 and on a Leonardo/Micro, digital 2