Here's the project I've been working on for the past few days. It's a fully working, 12-hour digital clock built in Minecraft using redstone and pistons. It uses 4 loops of piston memory daisy-chained together to count up from 1:00 to 12:59 and back to 1:00 on 4, 7 segment displays.

Hope you like it!

View of the display

All the redstone in the back

One of the 4 piston memory loops

P.S. If you want to see it, its at -550, -550 in the Creative world.