Strontium atomic clock

2016’s leap second hits tonight; finance and infrastructure sectors brace for impact

The world is about to experience its 27th leap second, a tiny but necessary change to the way in which we measure time that can cause a number of complications that belie the short nature of the alteration.

Although most people are barely aware of the change, in the past it has led to problems for major infrastructure, including mobile networks and electricity grids, as well as causing havoc in the stock markets.

The National Physical Laboratory (NPL) in London is the world’s official timesetter and keeps track of the Earth’s exact time, down to the millisecond, by using atomic clocks and observing changes to the planet’s rotation.

The atomic clocks used (below) are so precise that they currently only lose around one second per 138 million years. Despite this, work is currently under way on a new type of atomic clock that will lose around one second over the lifespan of the entire universe.

But altering the world’s official clock, even by a second, can cause an untold number of logistical issues in the battle to update the billions of time-keeping devices around the world.

The issues are largely caused by the irregularity of the leap second, which cannot be predicted in advance, unlike leap years that consistently happen every four years.

The leap second (and the leap year for that matter) allows parity to be maintained between the solar year, which is the time it takes for the Earth to circle around the sun (exactly 365 days, 5 hours, 48 minutes and 46 seconds), and the Gregorian Calendar (which lasts just 365 days).

Without this time shift, the Gregorian date system would fall increasingly out of line with the sun, eventually leading to summers in February and night time conditions at midday.

Dr Leon Lobo, strategic business development manager for NPLTime, explains the complex process behind inserting the additional second.

“With any leap second announcement there is a notice period which is provided six months in advance by the IERS, which is the organisation that monitors how the earth is rotating, and how it’s slowing down,” he said.

“As soon as the divergence between the mean solar day and the global time scale exceeds 0.9 of a second, a leap second is added or taken away.

“We then feed leap second insertions into the official UK time scale which informs the rest of the world. There are also similar labs globally to NPL in every developed nation,” he added.

Lobo said that while all of the 27 leap seconds that have been added so far are additions to the time scale, it would be possible for future leap seconds to actually be subtractions due to the unpredictable nature of the earth’s changing rotation pattern.

“It’s heavily dependent on the processes within the core of the earth, things like tidal friction etc., and as such is not deterministic,” he explained.

Despite the fact that the leap second process has already occurred 27 times in the past, issues still arise due to the inconsistent way in which organisations around the world implement it.

The second is usually implemented at midnight on either 30 June or 31 December, but firms use different techniques to actually insert it into their time scales. It is this lack of a standard procedure that leads to synchronisation issues.

For example, some smear that second across all the seconds of the day in which is it applied, some apply it before that point in time, while some will apply it after.

“In the past we’ve had entire network infrastructures fail because of implementation issues because the system either didn’t implement it or implemented it at the wrong time,” Lobo said.

“This includes mobile and internet networks. Last year for example, there was a problem in Brazil where many of the networks used a common device that failed because of the implementation resulting in many of their networks going down there.

“This year, strangely enough, some systems were programmed when it was first announced back in June to add it in at the end of December; but they actually added it straight away rather than wait. So they lost synchronisation when they first fed the information in, well before the leap second was supposed to be applied.”

2016’s leap second will be applied at the end of the New Year’s Eve countdown, with the last minute of the year featuring an additional second: “60”.

“Within a second, a lot happens,” Lobo notes. “Whether its hundreds of thousands of trades per second or major synchronisation issues on an energy grid or telecoms network.”

But NPL does what it can to get the message out. It uses numerous methods to communicate the exact time to firms that need it: radio signals, internet-based timing, satellite communications and more recently, NPLTime.

NPLTime is a fibre-delivered service primarily aimed at the finance sector that provides very high precision by continuously monitoring the delay of the timesetting signal at every point on the network being used to transmit it. Once it reaches its destination, the time is then offset by this calculated delay.

This essentially offers “a huge amount of clarity to the finance market by providing a common clock at the microsecond level”, a level of millisecond synchronisation that is simply not in place at the moment Lobo admitted.

“At that level no one has the same time in the finance sector but new regulation is driving this and we’re trying to help by providing new techniques for time dissemination.”

But in the future, the leap second could become a far less frequently applied leap minute or leap hour. This possible change has been considered for a long time and the outcome of these discussions should be clear in the next few years, Lobo believes.

When pressed as to whether this year’s leap second will cause similar issues to those seen in the past, Lobo is hopeful.

“There will be a lot of people cheering perhaps at the wrong time but the good thing about the implementation at the end of December, New Year’s Eve particularly, is things like the finance markets are closed,” he said.

“The previous one last year at the end of June was mid-week and although for the UK it was fine because it’s always at midnight over here, from the point of view of the Asia Pacific for example, it was right in the middle of their trading day. So this time round hopefully we won’t see any major events but we will be monitoring countdowns all over the world just to make sure.”

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