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Will June’s Leap Second Break The Internet?

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On 30 June 2015, all of the world’s electronic clocks will be adjusted forward by one second. The change is needed to realign digital time and astronomic time, to adjust for the slowing of the Earth’s spin. While seemingly insignificant, this change could result in a partial Internet meltdown.clock - fse blog

This raises the obvious question: why are the clocks being adjusted when it poses such a devastating risk? If it all goes wrong we can blame the scientists at International Earth Rotation and Reference Systems Service, who have suggested that a leap second is implemented to ensure that the time that we use matches the time recorded by astronomical measurements.

Unbeknown to most, the Earth is slowing down. The effect of the moon and the ocean tides is acting as a brake on the Earth’s rotation and this means that if world clocks are not adjusted, one day, in the far distant future, midnight will not happen until dawn breaks. To counteract this, every 18 months or so (usually in June or December) a leap second is added to planetary time to align atomic clocks and astronomical observations.

To accomplish this, a positive leap second will be introduced at the end of June. The sequence of dates of the Coordinated Universal Time UTC second markers will be:

2015 June 30, 23h 59m 59s
2015 June 30, 23h 59m 60s
2015 July 1, 0h  0m  0s

Because clocks do not record the 60th second, this essentially means that at midnight on June 30, time will pause for one second, or to put it another way, the final minute of the day will be 61 seconds long. What could possibly go wrong?

Computer systems do not generally like it when time is adjusted. Many operating systems will fail to communicate with other computers if the internal clocks are in conflict; this is why modern operating systems always automatically adjust their own clocks.

You may think that this is all scaremongering, but the previous leap second, when applied in 2012, resulted in several major computer networks crashing. Qantas suffered a two hour outage when the Amadeus airline reservation system crashed and Mozilla, Reddit, Gawker, LinkedIn, FourSquare and Yelp all suffered problems. Qantas had to manually check-in passengers and this resulted in flight delays of up to two hours.

Following the incident in 2012, Amadeus investigated the cause of the crash and found that it was “caused by the Linux bug triggered by the ‘leap second’ inserted into clocks worldwide on June 30th.”

Most of the world’s websites run on Linux servers, however, in the case of the Mozilla, the problem was caused by Java failing to adjust to the leap second and causing problems with the Hadoop open-source database platform. Rebooting computer servers mostly resolved problems and Mozilla released a patch to help prevent the problem recurring.

To err on the side of caution, Intercontinental Exchange, which runs seven clearinghouses and 11 stock exchanges, including the New York Stock Exchange, has decided to shut down all of its systems for 61 seconds on June 30, 2015.

Google’s Leap Smear

Google have developed an alternative solution, one that does not require them to shut down the Internet. They have programmed a “leap smear”, which extends seconds either side of the leap second window by a small amount so that time can literally carry on unheeded, albeit a little slower.

Do we really need leap seconds?

Not everybody agrees with that we do. Dr Felicitas Arias, who runs the time department at the International Bureau of Weights and Measures, believes that leap seconds are redundant. They were introduced to help maritime navigation, but today, maritime navigation uses alternative ways to assess rotational time.

However, time pedants, such as Peter Whibberley from the National Physical Laboratory, say that a decision to ignore the leap second would result in the “most fundamental change in timekeeping for hundreds of years”.

Without leap seconds, in time, the world’s clocks will fall out of sync with the Earth’s natural rotation.

Be prepared

Although we cannot be sure what repercussions the leap second will have, if any, it is advisable to take some precautions to ensure that you are ready for the worst case scenario.

The most important task is to ensure that all your data and programs are backed up. This includes images, documents and emails, as well as databases, websites and spreadsheets. It is good business practice to have a contingency plan in place at all times, however, few small businesses ever do.

The worst case scenario is that your current computers and computer programs experience an unrecoverable error following the leap second update. Although data should be secure, operating systems and applications used to access your data may fail.

It is important to remember that it is unlikely that there will be any major problems and that most IT service providers have already tested for this scenario. However, you can never be too safe and you certainly do not want to become the case study of a business that collapsed following a major IT outage.

Shut down before you go home

Most software companies have implemented fixes for the leap second, however, because time is so important in computer networks, it would be advisable to shut down all computer systems on June 30. If you run a business, ensure that all staff are aware of the need to properly shut down their PCs before going home for the weekend.

When you return to work after the weekend and boot up your PC, your computer will make a new “handshake” with the networks and everything should reconnect smoothly. Enjoy your extra second in bed on the 30th!

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