Timekeepers abolish leap seconds, warn of Y2K-scale internet of things disaster

General Conference on Weights and Measures votes to end leap seconds, citing risk from first ever negative leap second

By LineZotpaper

Published19 October 2026

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The world's foremost measurement authority, the General Conference on Weights and Measures (GCPM), has voted to stop using leap seconds. The body warned that adding or subtracting a second to align civil time with Earth's rotation could inflict widespread chaos on internet-connected devices, potentially costing as much to fix as the millennium bug did.

The decision came at the GCPM's 28th meeting last week. Leap seconds have been used since 1972 to keep Coordinated Universal Time (UTC) within a close margin of astronomical time (UT1), which is set by Earth's variable rotation. In recent years the planet's spin has unexpectedly accelerated, raising the prospect of the first ever negative leap second: a subtraction of one second.

The GCPM's resolution after the vote stated that 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 body estimated that preparing industry would require financial investment "similar to their preparations for the millennium bug" — a global remediation effort historians have put at $300–$600 billion.

The growing number of internet of things (IoT) devices was a major factor. The GCPM noted that "dispersed multi-sensor systems, smart grids, and virtual services" face "an increasing risk of malfunction" if any leap second is inserted, and that IoT devices from different manufacturers often lack consistent update mechanisms. It also pointed out that major service providers already use different methods to handle leap seconds, creating timing inconsistencies between systems.

To replace leap seconds, the GCPM approved a new scheme called "Continuous UTC", due to take effect next year. Under this system, UT1 and UTC will be allowed to diverge by up to 3,600 seconds — one hour — before a correction is required. The approach mirrors the familiar practice of daylight saving time, offering an off-ramp from the high-stakes second-by-second adjustments that carry the risk of a digital meltdown.

Analysis

Why This Matters

The decision spares the world a potential multibillion-dollar remediation effort for a negative leap second, which the GCPM said could cost as much as the Y2K bug.
It ends a source of timing uncertainty for billions of internet connected devices, many of which are difficult to update and could fail on a leap second.
The shift to Continuous UTC prioritises digital reliability over exact astronomical alignment, a tradeoff that will become more significant as Earth's rotation continues to vary.

Background

Leap seconds have been added irregularly since 1972 to keep Coordinated Universal Time (UTC) within 0.9 seconds of astronomical time (UT1), which follows Earth's variable rotation. As the planet's rotation recently sped up, timekeepers faced the prospect of a negative leap second for the first time. The GCPM, the international authority for measurement standards, considered the idea too risky and at its 28th meeting voted to end the practice.

Key Perspectives

GCPM: Argues that a negative leap second would pose a high risk of anomalies and disruption to critical infrastructure, and that preparing industry would require investment on the scale of the Y2K remediation effort, estimated at $300–$600 billion. Critical infrastructure operators and IoT manufacturers: The GCPM notes that many IoT devices lack robust update mechanisms, making them vulnerable to leap second failures. Service providers already use different mitigation methods, causing inconsistency in timing between systems. The new standard: Continuous UTC will allow civil and astronomical time to drift by up to one hour before a correction is required, ending the era of second-level alignment and providing a more resilient structure for modern computing.

What to Watch

The implementation of Continuous UTC next year and how telecommunications, finance, and internet industries adopt the new standard.
Whether the one hour drift limit ever becomes politically contentious, similar to debates about daylight saving.
How Earth's rotation behaves: a further acceleration could extend the timeline before the first hour adjustment is needed.

Sources

Time Lords kill leap seconds, before they become the new Y2K bug · www.theregister.com - Articles

Checked

12 claims in this story checked against 1 source: 8 supported.

Show each claim

SupportedThe GCPM voted to stop using leap seconds.www.theregister.com - Articles: “The matter came to a head at last week’s 28th meeting of the GCPM, at which Time Lords voted to end use of leap seconds.”
Partly supportedThe GCPM warned of a Y2K-scale internet-of-things disaster.www.theregister.com - Articles: “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”
SupportedThe risk of the first-ever negative leap second was cited as a reason for ending leap seconds.www.theregister.com - Articles: “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”
Not in the sourcesThe GCPM is the world's foremost measurement authority.
SupportedThe decision came at the GCPM's 28th meeting last week.www.theregister.com - Articles: “The matter came to a head at last week’s 28th meeting of the GCPM, at which Time Lords voted to end use of leap seconds.”
Not in the sourcesLeap seconds have been used since 1972.
Partly supportedEarth's rotation has unexpectedly accelerated in recent years.www.theregister.com - Articles: “In recent years, they have even pondered a negative leap second because Earth’s rotation has sped up a little.”
SupportedThe resolution said 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.”www.theregister.com - Articles: ““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,””
SupportedThe GCPM said the required financial investment would be “similar to their preparations for the millennium bug”.www.theregister.com - Articles: ““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.””
SupportedHistorians put the global cost of Y2K remediation at $300–$600 billion.www.theregister.com - Articles: “Historians now cite the global cost of Y2K remediation at $300-$600 billion.”
SupportedThe replacement scheme is called “Continuous UTC” and comes into force next year.www.theregister.com - Articles: “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.”
SupportedUnder Continuous UTC, UT1 and UTC may diverge by up to 3,600 seconds.www.theregister.com - Articles: “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.”