To begin the explanation, I would like to say that I have always wanted time to be metric. 5 o'clock would be mid-day, 7:5 would be three quarters (6:00 pm), and so on. This prototype tells deci-days, centi-days, and milli-days, in that order. For those that are unfamiliar, ten deci-days are in a day, ten centi-days are in a deci-day, and ten milli-days are in a centi-day. For comparison, a milli-day is 86.4 seconds.
With my limited supplies, I had to make it read in binary, but that's alright with me!
I am a beginner at Arduino. And a beginner at instructables. So at times it may not be perfect, and I hope you have some understanding!
Step 1: Supplies
12 leds. It helps if 8 are one color, and 4 are another, but that isn't all that important.
12 330 ohm resistors. 10k works too, but it makes the leds a bit dim.
An Arduino I have an Uno r3, but anything with 12 or more output pins will work.
A breadboard You could probably survive without one, but I would highly recommend one.