Today (November 2^nd) the International Telecommunication Union’s World Radiocommunication Conference meets in Geneva. It will run until the 27^th and, apparently, during much of that time, there will be bitter arguments about the leap second. As we discussed in Just a Second https://www.eejournal.com/archives/articles/20150924-justasecond/ a few weeks ago, now that we measure the second using atomic frequencies, it is clear that the earth doesn’t rotate evenly, so, at relatively unpredictable times, a leap second is declared. This requires the administrators of a range of systems to tell the system to add the extra second. The first time a leap second was declared, there were serious problems. Supporters of the leap second claim that the problem is well understood and manageable, but opponents argue that now we don’t rely on the sun and stars for navigation, and use artificial satellites and the internet to share time signals, there is no need to take any risks. The arguments are summarised in IEEE Spectrum.  http://spectrum.ieee.org/tech-talk/computing/networks/leap-second-heads-into-fierce-debate