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The leap second is being phased out. Why is the world changing how it keeps time?
Leap seconds could soon become a thing of the past as experts adopt a new approach to global timekeeping.
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The world is preparing to move away from the leap second, a tiny adjustment used to keep clocks in sync with the Earth's rotation. International experts have backed a change to the way global time is measured, with the new approach set to take effect in May 2027.
What is a leap second and why is it being scrapped?
According to The Guardian, representatives from 69 countries voted to replace the leap-second system with a more flexible approach to coordinating universal time.
To understand the decision, it helps to know that the Earth does not rotate at a perfectly constant speed. Its rotation is influenced by several factors, including movements within the planet, ocean circulation and atmospheric conditions. This means astronomical time and the time measured by highly precise atomic clocks can gradually drift apart.
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Atomic clocks form the basis of Coordinated Universal Time (UTC), the international standard used to coordinate clocks worldwide. Since 1972, 27 leap seconds have been added to UTC to keep it broadly aligned with the Earth's rotation.
However, these adjustments can create problems for digital systems. As The Guardian reported, a leap second added in 2012 caused some computer systems to freeze, while websites including Reddit and LinkedIn experienced outages. Qantas flights were also affected by technical problems.
The possibility of a negative leap second, which would require clocks to skip a second rather than add one, raised further concerns because many systems have never had to handle such a change.
Leap hour explained: How will the new system work?
The new approach will allow UTC to differ from astronomical time by as much as one hour before a correction becomes necessary. This is why the change is often described as a shift from the leap second to the leap hour.
However, this does not mean clocks will suddenly gain an extra hour in 2027. According to the International Bureau of Weights and Measures (BIPM), the decision allows the difference between UTC and astronomical time to reach 3,600 seconds, or one hour.
The continuous UTC system is scheduled to take effect on May 20, 2027. Any adjustment on the scale of an hour is not expected to be necessary for a very long time.
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Why does the decision matter?
Accurate timekeeping is vital for satellite navigation, communication networks, electricity grids and financial transactions. According to The Guardian, removing leap-second adjustments could reduce the risk of technical glitches in systems that rely on precise timing.
The change aims to make timekeeping more reliable for modern technology, even if it allows a larger gap between clock time and the Earth's rotation.
