Leap Second – Will More Websites Go Down?

time change

Tomorrow, on Tuesday, you are going to have a little more time on your hands when a leap second is added to the world’s clocks. A single leap second doesn’t seem like a big deal, however, in 2012, the addition of a leap second brought down websites run by Mozilla, Gawker and Reddit.

Technically, a leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time in order to keep its time of day close to the mean solar time. If a leap second wasn’t added to the world’s clocks, time as we know it in conjunction with the sun wou.ld gradually get more and more screwed up because of irregularities in the Earth’s orbit. Twenty-five leap seconds have been added since 1972, the last one being added on June 30th, 2012. Tomorrow’s leap second will be added at 23:59:60, Coordinated Universal Time (7:59 PM ET).

The leap second phenomenon doesn’t only offer added seconds to the world’s time, it is possible to actually ‘take away’ a second of time if need-be. However, in the 43 years since the invention of the leap second, there has yet to be a situation where time would need to be subtracted, and thus humans have only added leap seconds to Earth’s time.

So what was the impetus of the use of leap seconds? Believe it or not, television and radio. It was determined in 1961 that about 1.4 to 1.7 milliseconds are added to the days on Earth each century. Again, that doesn’t seem like a lot, but after a while it tends to add up. To compensate between International Atomic Time and time standards that are tied to the position of the sun, (like Greenwich Mean Time), the rate of some atomic clocks was consistently “slowed” between 1961 and 1971 to keep them consistent with solar-based clocks. Why was that so important? Broadcasts of radio and television around the world are based on solar-based clocks like Greenwich Mean Time.

In 1972, the leap second idea was introduced so that changes could be made less often to the world’s clocks and keep both solar-based time and atomic time in sync.

Like something akin to the Y2K Bug fears in 1999, adding a leap second to the Earth’s clock can cause some major issues. As stated at the beginning of this article, when the leap second was added in 2012, Reddit, Gawker and Mozilla all crashed. The reason? The time their websites run on is actually calculated in time periods shorter than a second. Hence, when the leap second was added, the programs and algorithms the websites function on got uber-confused, and ceased to function.

Will that happen tomorrow when the 26th leap second is added? We shall see.

Photo by Cleland Rimmer/Getty Images