Made this clock the other day as it was the only thing I could understand, it was simple and I had parts. Hats off to Nick for passing on the info so clearly. I did find one problem. The center digit segments (SEGG) were not lighting properly and the whole thing seemed buggy (like a bad ground or a pin floating) but I could not put my finger on it. Finally I found the trouble. I cannot explain the "why" but apparently having the SEGG on pin13 is not good in this case. I noticed the SEGG in digit 2 flash as I uploaded, it was in sync to the led on pin13 on my boarduino. So, I switched the alarm led and SEGG pins, pin8 and pin 13, and it fixed the problem.
I also have a question. I'm not a programmer (I just started using Arduino IDE this week and I have no previous experience beyond Basic stamp and lighting leds) so bear with me on my lack of proper usage of terms etc.
Question: My display has the 4 decimal points AND a colon. The colon is treated like another digit as I understand things. I can't figure out how to flash it instead of the decimal point. I think I need another output pin and then I'm lost on the code although it looks like it has something to do with the switch statements/functions/procedures? Any advice would be helpful and thanks again.