“Leap second” will be phased out by 2035 as it could wreak havoc on GPS and telecoms | Wbactive

While we all know about the extra day in February during a leap year, there is another timekeeping change we make to our watches that you may not have heard of.

This is the “leap second” – an extra second that we attach to the year to ensure that Coordinated Universal Time (UTC) exactly aligns with the Earth’s rotation on its own axis.

However, scientists have now agreed to eliminate the leap second and let the two get out of step.

The decision was made because that extra second can cause problems for digital systems that rely on a regular flow of time, such as GPS and telecommunications.

We will ditch the leap second by 2035, but it’s not decided for how long, and some scientists say it won’t be added again for at least a century.

Since 1972, a leap second has been added to astronomical time whenever the gap between it and Coordinated Universal Time reaches 0.9 seconds, which is unpredictable


A leap second is an adjustment of a single second to Coordinated Universal Time (UTC).

This is to keep atomic clock time and solar time inline.

There is a difference between the incredibly accurate International Atomic Time (TAI), measured by atomic clocks, and the inaccurate Observed Solar Time (UT1), which is related to the Earth’s rotation.

The UTC time standard, which is equivalent to Greenwich Mean Time (GMT), is widely used for global timekeeping, including in astronomy.

Without the leap second, which is added every few years, UTC would no longer be in line with the Earth’s rotational speed.

While this would be imperceptible to most people, it could shift the noon point and impact the internet for hundreds of years.

It’s not a popular practice, however, which is proving disruptive to some internet services, as Google “smoothes” the time over a year to add the increase in microseconds to each day.

International standards bodies responsible for the time are debating whether to drop this practice as it would only deviate by about a minute even over 100 years.

A document from the 27th General Conference on Weights and Measures (CGPM) states: “The…introduction of leap seconds creates discontinuities that can cause serious malfunctions of critical digital infrastructures.

“Operators of digital networks and GNSS [Global Navigation Satellite System] Systems have devised and used various methods of introducing leap seconds that do not conform to agreed standards.

“Using these different methods also creates confusion, which threatens the recognition of UTC as the sole reference timescale.”

UTC is defined by atomic clocks around the world ticking precisely and continuously.

However, these atomic clocks do not exactly match observed solar time, which historically defines days as a single rotation of the Earth.

The time it takes for a single planetary revolution changes from time to time due to the moon’s gravitational pull, causing the two time systems to drift apart.

Since 1972, a leap second has been added to astronomical time whenever the gap between them reaches 0.9 seconds, which is unpredictable.

Since then, this has happened 26 times, the last time in 2016.

Since 2020, however, the earth’s rotation is said to have accelerated.

Therefore, in the future, a leap second may need to be removed rather than added to keep observed solar time in sync with clocks.

While the addition of a leap second goes unnoticed by most, it has caused problems for the International Bureau of Weights and Measures (BIPM), the body responsible for UTC.

These arise from differences in the way clock representations interpret the leap second and how some clocks even miss its inclusion.

At this year’s CGPM, which takes place every four years in the Palace of Versailles near Paris, the metrologists agreed that the leap second must go by 2035.

While it will be added as needed until then, thereafter astronomical time and UTC will be spaced apart by more than a second.

They also suggested that we should wait at least a century before reapplying, so the two are out of sync for about a minute.

The decision on this cap, if any, will be finalized by 2026.

Representatives from the US, Canada and France pushed for the change, although Russia voted against the proposal to eliminate the leap second in 2035.

The Russian satellite navigation system GLONASS already includes the leap second, which means that significant technical changes have to be made.

However, GPS is powered by atomic clocks by the US military and virtually ignores the extra second.

The decision was made because this extra second can cause problems for digital systems that rely on a regular flow of time, such as GPS and telecommunications (stock image).

The decision was made because this extra second can cause problems for digital systems that rely on a regular flow of time, such as GPS and telecommunications (stock image).

On June 29 of this year, Earth reported its shortest day on record, shortening its usual 24-hour rotation by 1.59 milliseconds.

This raised the prospect that a negative leap second must occur to keep the clocks aligned, which would be the first time in history that global clocks have been sped up.

This was “never considered or tested,” according to CGPM documents, and supported the decision to eliminate the leap second.

Scientists claimed that climate change, seismic activity, and ocean circulation could all be responsible for the faster rotation.

It could also have been the result of the moon’s gravitational pull and what is known as the “Chandler Wobble” – a change in the Earth’s rotation about its axis.


Atomic clocks have a timekeeping mechanism that uses the interaction of electromagnetic radiation with the excited states of specific atoms.

The devices are the most accurate timing system we have, using consistent standards.

They are the primary standards for international time distribution services and are used to control wave frequency for TV, GPS and other services.

The principle is rooted in atomic physics and measures the electromagnetic signal that electrons in atoms emit when they change energy levels.

Modern versions cool atoms to near absolute zero by slowing the atoms down with lasers. With the temperature of the atoms determining their accuracy.

Every few years, a “leap second” is added to atomic clocks, effectively stopping them for a second to match the speed of the Earth’s rotation.


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