Prototyping area for soldering connectors, circuitry or sensors Adafruit libraries and example code for both SD and RTC mean you can get going quickly On board Real time clock (RTC) keeps the time going even when the Arduino is unplugged. The battery will last for years. Works with Arduino UNO, Duemilanove, Diecimila, Leonardo or ADK/Mega R3 or higher. ADK/Mega R2 or lower are not supported.