|# of units||Price|
This is a great battery-backed real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed or if the power is lost. It's perfect for data logging, clock-building, time stamping, timers and alarms, etc. The DS1307 is the most popular RTC, and works best with 5V-based chips such as the Arduino.
This breakout board is a kit and requires some light soldering which should only take about 15 minutes. Please check the documentation page for a list of parts and assembly instructions. Schematic and layout files are at GitHub
The DS1307 is simple and inexpensive but not a high precision device. It may lose or gain up to 2 seconds a day. For a high-precision, temperature compensated alternative, please check out the ChronoDot.