YouTube User SLvik78
John found a great dekatron based Nixie clock on YouTube that I wanted to re-post here. All of the timing is derived from the mains line at 50Hz. The dekatrons divide the time base in to seconds, minutes, and hours. I've contacted owner and others have as well to see how he performs the "divide by 5" function to get 1pps and the "divide by 6" to convert 60 seconds in to a minute. You can see the jump/division happen at 1:20 seconds in the video. I am not sure if this is simply a matter of wiring the dekatrons differently or there are other components in use that are not visible.
If you have an idea how this works, please leave a message in the comments and I will update this post.
Be sure to read
Lastly, be sure to check out Kahlo's link for his schematic of a 50Hz divide by 5 & 10 design. This help quite a bit: http://kahlo.redirectme.net/~kahlo/forum_jogi/Dekatron_Zeitbasis.png (thanks for sharing!)