So you are planning to make a wristwatch, and not a clock? Just letting you know, that will be a very difficult project and probably cost several thousand dollars to develop, and the power supply will be especially difficult. If you are building a full-sized clock, there are plenty of nixie power supplies available on ebay for very cheap, but if I remember you are in Eastern Europe and it is difficult to ship there. In that case, a simple boost converter will work. I think I posted a link on your other thread, but if not, check out http://sites.google.com/site/willyager/nixie-clock
. Simply do some research on boost power supplies (I got started from ladyada's VFD "ice tube" clock power supply, she even has a great power supply calculator), and you should be able to replace the ATTiny45 in my schematic with an arduino. BTW, a great way to learn about this is to google for "nixie schematic", "nixie power supply", "nixie multiplexing" etc.