Real Time Clock/RTC DS1307 I2C - clock breakout board/module
Product information:
A clock for your Arduino! With this module your Arduino always has the correct time and date, even when the power goes out.
Because the clock has its own battery it will always keep running. Up to 7 years on 1 battery!
The clock is connected via the I2C bus. So simply connect the power supply, SDA and SCL to your Arduino, run the code and you are up to date!
By means of RTCLib you don't have to do much more than set the clock and read it out. (See the programming examples under the documentation tab.)
You can also find a good explanation of I2C on YouTube, just search for 'Jeremy Blum I2C tutorial'.
Dimensions: 2.9 x 2.6cm
If you are not using a rechargeable battery, use 3.3V as Vcc or remove R4, R5 and D1 and replace R6 with a piece of wire. (Modification at your own risk.)