Now that the gauges are working you need some code to make a clock. I originally wrote a routine to keep time based on the internal oscillator of the arduino but was not satisfied with the accuracy. I researched real time clock chips and found the DS 3231. It is really an easy to use and amazingly accurate little chip. It also is battery backed up and keeps the month date day of the week and year. This was important to me because I wanted to add a routine to calculate and display the moonphase based on the current time and date. Another important feature is that it outputs a 1Hz square wave that can be used to trigger the updating of the gauges. Just the ticket! And all over I2C!
I found a really convenient little board called the chronodot that contains the DS3231 chip, battery slot, battery and circuitry in a dip format board. Very convenient. You don't have to use this, as a matter of fact, the first one I set up I used the DS3231 chip soldered to an SOIC to DIP adapter board and a separate battery holder. I like the chronodot much better because it is all integrated and ended up being much smaller too.
Here's a link to the chronodot manufacturer: