I think we've accumulated enough reasons to want 2016 to leave as soon as possible… but guess what? This year will continue to resist, even in the smallest details. I mean that the International Earth Rotation and Reference Systems Service (IERS) has established the need to add a leap second on December 31, just as it happened last year on June 30. That second may be insignificant for human activity in general, but digital systems have a different opinion…
On December 31 at 23:59 with 59 seconds, we will have to count the next second as '60' instead of '00'. Well, let's be honest: more likely than not, no one will do that, except those dedicated to keeping our clocks right. Why does this happen? Where does the leap second come from, or simply leap second? If we compare the precision of atomic clocks tied to Coordinated Universal Time (UTC) with the precision of Earth's rotation, the truth is that clocks win by a landslide. "More than a million times better," according to Peter Whibberley, a researcher at the UK's National Physical Laboratory. Earth's rotation suffers slight fluctuations that cannot be fully anticipated, and the leap second emerges as a calibration resource between civil time and solar time.
It seems like too much history for a single second, but the truth is there's much more. The debate about the existence of the leap second has spanned years, and no agreement has been reached yet. Due to the unpredictable nature of the leap second, it needs to be scheduled manually, causing those responsible for critical systems to pull their hair out. IERS communicates the change with six months' notice, giving enough time for necessary adjustments; however, the whole process can be very traumatic. The leap second of summer 2012 affected entire sites, hung servers, required emergency patches, and even brought down an airline reservation system.
Now, think about things like electronic transactions and geolocation systems. The consequences could be even more serious… but the world keeps arguing. The conflict is so broad that the United Nations decided to kick the can down the road and delay any decision until 2023. What will be done in the meantime? Google's technique is very interesting: Reduce the speed of its NTP clocks by 0.0014 percent during the ten hours before and the ten hours after the leap second, so that it is smeared so to speak.
