Timekeepers Vote to End the Leap Second by Next May

Timekeeping has changed forever after a decision by an intergovernmental organization that determines measurement standards to end what is known as the leap second. Here is a look at the leap second and why it is going away.

International Timekeepers Vote to End Leap Second

The 69 member states of the International Bureau of Weights and Measures (BIPM) voted last week on a resolution that has effectively ended the leap second. The vote happened in Versailles, France, with the resolution set to take effect in May of 2027. The majority of the nations voted for the elimination. Russia voted against the proposal, and Belarus abstained.

The leap second is a tiny link between the rotation of the Earth and the world's time standard. The minuscule measurement of time is used for various infrastructure purposes, such as in power grids and telecommunications systems. The leap second has been inserted into global clocks only 27 times since 1972.

By inserting the leap second, astronomical time and the Coordinated Universal Time (UTC) are able to run in sync with each other. For further context, UTC is the global time-telling standard set by atomic clocks that were first launched in the 1950s, while astronomical time is based on the Earth's rotation and measured by observatories.

Because the Earth is known to wobble, it is not always the most accurate time-teller. Last week's vote to end the leap second essentially sends the message that the world is now going to follow the more stable man-made clocks rather than leaning on the astronomical clock.

Proponents of ending the leap second argued that the Earth was becoming less reliable due to the impacts of climate change. For example, the acceleration of the melting of the polar ice caps at the hands of global warming has been amplifying this wobble effect.

For years, leap seconds were the compromise between the two time-telling systems. You likely never noticed the leap second, as they happened at irregular intervals and were only announced with six months' notice. However, the insertion of these little seconds often created issues for data server operators and pieces of infrastructure that needed exact timekeeping to avoid disruptions.

What Happens Next?

Last week's meeting in Versailles was the first time since 2022 that the BIPM met to discuss these timekeeping issues. The debate over whether to eliminate the leap second took on more urgency in those four years as it became evident that it would soon be necessary to subtract a second rather than add one. This concept is known as the negative leap second.

Scientists said that the negative leap second would have been needed because although the long-term trend of Earth’s rotation is slowing, it is actually accelerating in the near term. This means that timekeepers would have needed to subtract a second from the UTC to line up the atomic and astronomical clocks.

Experts warned that having to delete a second would likely cause mass disruptions in today's increasingly digital world. BIPM members said that the world is unprepared for this type of move, equating it to the preparations leading up to the turn of the century in Y2K.

BIPM is now considering adding what is known as the leap hour. This initiative would allow atomic time to separate from astronomical time, making international timekeeping independent of the planet's rotation.

Although leap seconds are a thing of the past, a leap hour could be added to accommodate the growing difference between atomic and astronomical time. Scientists with the BIPM explained that the maximum difference between atomic and astronomical time should never exceed 3,600 seconds or one hour.

However, it would take more than 3,000 years for this type of delta to take place. This means that this leap hour would not need to be added for another 3,000 years. In short, the BIPM is recommending passing this problem onto generations way down the road. Who knows what time will look like at this point in the future?

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