A consensus can't be reached on whether to get rid of the leap second or keep it

Sep 21, 2013 13:31 GMT  ·  By

The world's timekeepers are trying to figure out whether to continue to use leap seconds, which were introduced four decades ago, or to scrap the idea altogether. Leap seconds are used to adjust the world's standard time to the actual solar time.

The Earth's rotation speed varies in time, influenced by climate, geological events, such as earthquakes, and other factors. This variation can't be predicted, but a day five years from now may be longer or shorter than it is today.

So, for the past four decades, a leap second has been added, a total of 25 times, to make up for the discrepancy. All the leap seconds so far have been added, but one may be subtracted as well, if there's a need.

This practice keeps the standard time in sync with the actual solar time. Scientists estimate that without leap seconds, a discrepancy of some 15 seconds would accumulate every 100 years.

The problem though is that this leap second can cause problems with computer and network systems, which operate at time scales well below the second. Leap seconds have to be added manually to each system. This can cause problems for software which wasn't designed to handle leap seconds or, more likely, when trying to sync two computer systems operating according to a different time.

The bigger problems are when trying to calculate how much time has passed since a previous date, since leap second tables have to be consulted. The unpredictability of leap seconds also means that dates and time tables can't be compiled for more than six months in advance.

Google came up with a very ingenious solution last summer when the last leap second was added. The company simply made each second on the day the leap second was supposed to be added slightly longer, so that, over the course of 24 hours, the leap second would be accounted for while its computer systems would still count 86,400 seconds in a day.

But not everyone has Google's engineers, the massive infrastructure or the technical know-how to pull this off. So the discussion now is whether to abandon the leap second altogether or to keep it.

The International Telecommunication Union, which among other things handles time standards, has convened in Geneva for week to try to reach consensus. A decision must be agreed upon by 2015, but the different sides couldn't reach an agreement as the talks ended.