You write a C program to display the time.

I'm mostly joking, but it does depend on the program it's running. I think most of them go to sleep to conserve battery so you have to push the button to wake it up.

It might be cool to have an accelerometer so you could shake to display the time (and do things like tracking your motion like Fitbit)

There is a smaller clock that is always displayed on the screen so you don't need to press a button to view the time. You also have the option to always have the larger clock displayed - at the expense of battery life. These features and a ton more can all be customized through an app that is installed on the smartphone.