Used 6 IN12b Nixie Tubes from Ebay. The board is powered by a common 5V 2A wall adapter. Because I wanted to use 5V I have used a 5V to 170V flyback converter, could have used a boost converter but a set up from 5V to 170V is a bit too high for a boost converter. The Nixie Tubes are controlled using 200V MOSFETs and a few serial to parallel converters which are all connected together. This allows the Raspberry Pi to to use its SPI port.
I used a Raspberry Pi because it is easy to set up WiFi and get the time from the interent. The real time clock I used is also already supported by the Raspberry Pi. The real time clock has a coin cell battery back up.
A python program running on the Raspberry Pi just gets the current time from the operating system and turns it into a form to send to the serial to parallel converters before sending it to the SPI port. And repeats.