Plate Nº 14 · recorded October 16, 2026
PhysicsReported finding
Leap Seconds Scrapped: World Timekeeping Shifts From May 2027
From May 20, 2027, leap seconds will no longer be added to clocks worldwide. The change lets official time drift up to an hour from Earth's rotation to keep technology running glitch-free.
By Marcus Bennett3 min read593 words
In brief
- Leap seconds will no longer be added to clocks starting May 20, 2027.
- The General Conference on Weights and Measures adopted the resolution on October 15, 2026.
- UTC will be allowed to drift up to one hour from Earth-rotation time before any new adjustment.
- The resolution cited a 30% chance a negative leap second would have been needed by 2035.
- Earth's uneven rotation, driven by internal movements and the Moon's gravity, forced the occasional one-second corrections.
Starting May 20, 2027, the world's official time standard will stop adding leap seconds — a decision the General Conference on Weights and Measures adopted at its annual meeting on October 15, 2026. The resolution, published by the Bureau International des Poids et Mesures (BIPM), removes an adjustment that has occasionally disrupted computers, satellite navigation, telecom networks and power grids.
The change is small in scale but large in consequence. For decades, timekeepers have inserted an extra second into clocks to keep civil time aligned with Earth's uneven spin. Now that practice ends.
What does the ruling change?
Under the current rules, Coordinated Universal Time (UTC — the time standard behind civil clocks worldwide) must stay within one second of UT1, the time based on Earth's rotation relative to the sun. Each time the gap approached that limit, the timekeepers would add a leap second.
The new resolution widens that tolerance dramatically. UTC and Earth-rotation time may now drift apart by as much as one full hour before officials would consider adjusting clocks again.
How long would that take? Probably centuries — but nobody can say for certain, because Earth's spin does not behave predictably. Movements of material inside the planet and the gravitational pull of the Moon both speed the rotation up and slow it down in ways scientists cannot forecast over long spans.
Takeaway: clocks will run continuously, and the gap between official time and the sun's position can grow to an hour before anyone intervenes.
Why is a leap second a problem?
We define time with atomic clocks, which keep near-perfect, steady seconds. Earth's rotation is messier. The planet's spin rate fluctuates slightly, so the day is not a fixed length in atomic-clock terms.
Leap seconds were the patch. By adding one second — 27 such insertions have occurred since the system began — timekeepers kept UTC within the one-second tolerance of solar time. More recently, they had even discussed the opposite: subtracting a second, if Earth's rotation sped up enough.
That subtraction scenario worried engineers most. The resolution noted a 30% chance that a negative leap second would have been needed by 2035. Software that has never handled a missing second would face an unprecedented test. Anyone who remembers the Y2K scramble has a sense of how much trouble a single misplaced digit in timekeeping can cause across global systems.
Takeaway: inserting a second already caused glitches; deleting one could have caused worse, and the odds of needing it by 2035 had reached 30%.
What happens to everyday time?
Almost nothing, at first. No one will notice a difference in daily life. Over a very long period, the drift between clock time and the sun's position in the sky might eventually become measurable — but sunrise and sunset already shift with the seasons, and daylight saving time already jumps our clocks by an hour, so exact alignment with the sun is not something we currently experience anyway.
The real beneficiaries are the systems that depend on smooth, predictable time:
- Computers and data centers, which must never see the same second twice — or a second vanish.
- Satellite navigation, which depends on precise timing to compute position.
- Telecommunications networks, which synchronize handoffs between towers and switches.
- Power grids, whose protective relays time their switching decisions.
For these operators, the removal of leap seconds eliminates a recurring source of risk. Time will march on, now without interruptions.
Takeaway: for people, nothing changes; for the technology that runs on continuous time, one recurring glitch source disappears.
via bipm.org (Original)
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News editor covering regulation, policy and their impact on general science news at SciBeat.
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