This is not an Instructable how to recreate the clock project that got Ahmed Mohamed in trouble in September 2015, nor do I want this to be a discussion about what happened. What I do want to do is lay out a simple clock project using an Arduino to help inspire people like Ahmed to keep hacking, making, and programming.
At it's most fundamental, a digital clock is a computer with input and output and with behavior controlled through logic. Using an Arduino, we can program and test the behaviors step by step. This can lead us in to some insights as to why the basic digital clock hasn't changed in several decades. It can also let us creatively explore some alternatives.