The RTC Pi Plus is a real-time clock backup battery module for A , B and Pi 2 Model B. It keeps track of time while the Raspberry Pi is off.
The RTC Pi Plus is powered by the host using the Raspberry Pi GPIO and extensive GPIO pins on the connector allow you to stack the RTC Pi more with other expansion cards. The RTC Pi Plus uses the real-time clock DS1307 RTC and a CR2032 to maintain the date and time.
Unlike most other depending RTC DS1307 RTC modules Pi also includes an I2C logic level converter allowing you to connect to other 5V I2C devices to your Raspberry Pi.