10 Jan 2015
As shipped, the Pi has no real-time clock, and depends on the internet to determine the current time. Since my Pi might run without internet, I added a real-time clock to it. It's an off-the-shelf DS3231 (http://goo.gl/BKyjT9) unit with removable battery that plugs directly into the pi's headers, tapping the i2c bus and 3.3V power and ground.
To enable i2c on the Pi, so that it can read data from the RTC, you need to:
run "sudo raspi-config"chose item "9 advanced options"choos...