Big thanks to Evan Quirk for sending in his complex NTP Synced Nixie Tube Clock, best of all there is full details provided so that you can learn from it.

"Constructing a clock using nixie tubes is nothing new. It has been done countless times, to the point where it is almost considered a rite of passage for an amateurs in electronics. I was interested in building a nixie clock, but I wanted to do something different, something you couldn’t find in a kit. Eventually I decided on building a nixie clock that would be able to fetch the time automatically. I decided to do this via NTP. By deciding to use NTP for time synchronization, I decided that software would be a significant design aspect. The software would have to have knowledge of TCP/IP protocols, mainly UDP for NTP synchronization. The software would also have to convert the UTC time into format suitable for output. Hardware would have to include all components needed for display as well as those for network communication."