This submission shows how to use Simulink with Arduino Support package to build a binary clock.
What's a binary clock?
https://en.wikipedia.org/wiki/Binary_clock

Several things that can be learnt here include:
1) Using clock block to generate the time.
2) Separating the time value(a number) to individual digits, using the 'fix' and 'mod' function.
3) Converting the decimal value to binary values with a Matlab function block.
4) Sending the binary values to LEDs via digital output pins.

There are 4 sets of 4 LEDs (total 16 LEDs).
Orange is in hundredths of a second, Blue in tenths of a second, green in ones(0-9) and Red in tens.

This model is easily configured to include hundreds if needed.