I am not the most experienced with Arduinos/circuits/programming, but this is how I would tackle the project. First I would decide whether or not the project seems possible. From what I read, I see nothing that should prevent this idea from working. The only issue may be the inaccuracy of an Arduino keeping time. Without the use of a real time clock, your Arduino may drift off several seconds a day. Next step is to build it. It is not clear to me whether you built or wired up the project yet. If you have not, I'd say get it constructed because there are no foreseeable obstacles that would force you to abandon the idea. Once constructed, I wouldn't worry about time keeping until I knew I could control the LEDs as desired. Start with a 2D byte array to store the states of LEDS. Value of 0 = off, 1 = on. Initialize the array with some pattern and write a function that when called flashed those LEDs once. Call it in a loop and make sure the pattern you wanted to be displayed is displayed properly. Next write a function that takes hours and minute values and modifies the 2D array in a way the represents the time you want to show. Test it by calling it once with test values and then calling the display function repeatedly. Only once that works, would I bother with keeping time.
My final routine would look something like this:
byte ledPattern[5][3];
long nextTimeUpdate = millis() + 1000;
int hours = 12;
int minutes = 00;
int seconds = 00;
loop()
{
if (nextTimeUpdate >= millis()) //if a second has passed
{
updateTime(); //adjusts hours and minutes and seconds to current time
timeToPattern(); //set array pattern to represent current time
//Schedule next time update for one second
nextTimeUpdate += 1000;
}
flashLEDpattern();
}
I hope this helps. Again, I am not very experienced either so I hope I am not leading you in a wrong direction.