SparkFun real-time clock (DS1307)

The SparkFun real time clock (RTC) uses DS1307 to keep track of the current year, month, day, and time. The module comes already assembled as well as programmed to display the correct time and is equipped with a small CR1225 lithium battery lasts up to 17 years. The DS1307 is accessible through the I2C protocol. The package includes a test kit that serves as a guide for connecting the module to microprocessors using the I2C or BCD interface.

Arduino is an open-source platform for simple design and development of electronic programmable devices. It allows yout to build your own prototypes, control and control applications, serious monitoring devices with various sensors or a remote-controlled robot. And all this without the need for deeper knowledge of electronics. The Arduino Starter Kit is an introduction to the basics of electronics, where you can experience the Arduino platform. The parts in the Arduino package help you quickly design your own projects and implement them immediately. 

Properties:
Connection for 2 I2C wires
Hour, minutes and seconds indicator
Days, months, years
Leap years
Accurate calendar for until 2100
Built-in battery
1Hz output pin
56B of memory

Dimensions:
20 x 20mm