This is a simple binary clock. I was unable to find out that I particularly liked, so I decided to create one of my own.
This version does away with the buttons formerly on the screen, utilizing only a gear button to bring up user options. The result is a much cleaner interface, providing fewer distractions.
With respect to the time format, if your device is set up for 12-hour time, you can freely switch between either 12-hour or 24-hour time. If your device is set up for 24-hour time, you will have to completely exit the app, set up your device for 12-hour time, then run the app again.