Danrufus,
While in the army during the early seventies I used a computer that utilized Nixie tubes in its' display. When running a system check of some sort all of the tubes would cycle through all possible illumination configurations. It was pretty impressive looking so I made a point of initiating the process to impress people whenever I had the chance. The "Field Artillery Digital Automatic Computer" (FADAC) was used for determining azimuth, elevation, and etceteras.
Good luck with your clock project!
DimBulb