时间领主废止闰秒，以防其成为新的千年虫

Time Lords kill leap seconds, before they become the new Y2K bug

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Cite difficulty of updating IoT devices as major reason to stop adding time

The Time Lords at the General Conference on Weights and Measures (GCPM) * have decided to stop introducing leap seconds, citing the likelihood they could cause problems with internet of things devices – and therefore a Y2K scale remediation effort – as a reason for the change.

As The Register reported last week, the GCPM works to harmonize Universal Time – UT1, which boffins calculate using the changing speed of Earth’s rotation – and the Coordinated Universal Time (UTC) standard that humans use to set time.

We big-brained hominids can set standards but can’t do much about the fact that the speed of Earth’s rotation is variable. When our planet’s spin slows, the GCPM adds leap seconds so that UT1 and UTC are in synch. In recent years, they have even pondered a negative leap second because Earth’s rotation has sped up a little.

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Like all good standards orgs, the GCPM conducts years-long debates about its work. The topic of leap seconds has very much been on the agenda in recent years, as they’re increasingly hard to implement now that humanity relies on billions of devices that can usefully share the same timing data but may not easily account for leap seconds.

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The matter came to a head at last week’s 28 th meeting of the GCPM, at which Time Lords voted to end use of leap seconds.

The possibility of a negative leap second seems to have been a major factor.

“A negative leap second has not previously been applied, and it is considered to pose a high risk of causing anomalies and disruption to critical infrastructures that are largely unprepared,” the Time Lords wrote in a resolution posted after their vote. “The preparation would create, for the industries that rely on time synchronization, a need for financial investment, whose amount is estimated to be similar to their preparations for the millennium bug.”

Readers may recall that in the late 1990s, the world spent billions of dollars remediating software that, due to sensible-at-the-time memory-saving measures from the early years of business computing, couldn’t comfortably handle dates after December 31, 1999.

Historians now cite the global cost of Y2K remediation at $300-$600 billion. It's widely thought that money was not well-spent.

The GCPM also worries about connected devices.

The growing influence of IoT (Internet of Things) technologies, dispersed multi-sensor systems, smart grids, and virtual services for contemporary society, creates an increasing risk of malfunction in operation of systems and services with the insertion of any leap second, especially with a negative one,” they wrote.

Another concern raised in the resolution is: “The use of different mitigation methods for leap second introductions by global service providers in their server systems, in order to avoid time steps, leads to inconsistency in timing between different systems and in the disseminated time and frequency, which do not conform to the SI unit [the standard second].”

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The world is home to myriad manufacturers of IoT devices, but fewer standards on how they should behave. Some manufacturers therefore build shabbily insecure devices that ship with vulnerable software that allow them to be subverted with malware, or without facilities that allow easy updates. Billions of devices could therefore fail to implement a leap second.

That would become a problem because digital certificates include a notbefore value – a time before which the cert won’t be accepted. Many systems that see a misbehaving cert would reject it. It’s therefore conceivable that if a major ISP’s modems could not accommodate a leap second, the extra sliver of time’s introduction could see the carrier’s network decide its own customers are not trustworthy enough to connect.

Scenarios like that rather suggest Time Lords have taken a sensibly long view regarding the perhaps-inevitable fallibility of software developers.

The GCPM's replacement for leap seconds is to allow UT1 and UTC to diverge by up to 3,600 seconds under a scheme called "Continuous UTC" that comes into force next year. Humanity has lots of practice adding and removing hours thanks to Daylight Saving time, which some want to sunset . ®

* The organisation’s formal name is the Conférence générale des poids et mesures, which yields the acronym GCPM