NavList:

It's that time again. The international time-keeping system is about to bust sexagesimal counting again by adding an extra second to the last minute of the year. The final minute of 2016 will be 61 seconds in length. This will delay the arrival of 2017 by that one second allowing the Earth's rotation to catch up to the slightly over-swift passage of seconds under the modern definition of time and its recording by highly accurate atomic clocks. 

Here's a nice article discussing some of the problems caused by the addition of leap seconds to the calendar:
crn.com article.

Contrary to occasional rants by folks who misunderstand the issue, the removal of leap seconds would have no serious impact on celestial navigation. It would simply be an offset, a "watch error" that would be subtracted as appropriate (more on this in my AAS paper). If you think you're keeping the world safe for celestial navigators by supporting leap seconds, you're grossly mistaken. You're defending a false flag. Meanwhile, there have been recurring problems with other navigation systems, like GPS receivers, thanks to the issues that arise when leap seconds occur. Leap seconds are bad for navigation.

Frank Reed
ReedNavigation.com
Conanicut Island USA