Leap second could go by 2027. What it means, as timekeepers gather in Versailles

A timekeeping meeting on Thursday in Versailles near Paris could change how time works on Earth forever. The agenda is a decision on whether to scrap the "leap second". If that happens, then it would mean that the time we follow will be disconnected from Earth’s rotation and realign timescales.

Earth completes one rotation in 24 hours, and this is how the world's clocks are set. However, it occasionally wobbles, and the rotation is also slowing down gradually. This led the world's timekeepers to add a leap second every few years to ensure the clocks and Earth's rotation remain synchronised. The last time it happened was in 2016. But certain industries that rely on precise timing, as minute as milliseconds, argue it creates problems for them.

How time works right now

Coordinated Universal Time (UTC) is the global standard time based on high-precision atomic clocks that observe the vibration of atoms to mark the time. However, this is different from Earth's rotation. A leap second balances this gap. The first time this was done was in 1972. Since then, a total of 27 leap seconds have been added, with the last one on December 31, 2016. Leap seconds occur at the end of December or the end of June.

National Institute of Standards and Technology (NIST) has justified the need for leap seconds, saying, “The speed of the Earth’s rotation is not constant. …. This gradual decrease in the rotational rate is causing the duration of the mean solar second to gradually increase with respect to the atomic second.”

The problem with leap second

Certain industries depend on precise timings, and there have been instances in the past where the leap second created major problems. In 2012, LinkedIn and Reddit crashed because of it, followed by a collapse in ticket bookings for Qantas airline the same year. Australian Securities and Investments Commission warned against it in 2015. Meta also said in 2022 that each leap second is a "major source of pain for people who manage hardware infrastructures."

The International Bureau of Weights and Measures decided in 2022 that the leap second will be scrapped by 2035. However, Russia wants the timeline pushed to 2040 since it incorporates it into its GLONASS satellite-navigation system, and needs time to update its satellite systems.

Sixty-nine member countries are meeting to vote on scrapping the leap second by 2027.

Discussions will centre around three points. First, whether atomic clocks are still the most accurate device since optical frequencies are now more precise. Second, whether the leap second should be scrapped. And third, synchronising how time is measured on Earth with a new time standard being developed by NASA for the moon.

Will everyday life be affected if the leap second is ended?

NIST says that " adjustments would have to be made to time stamps and legacy equipment and software which synchronise to UTC for astronomical observations.” Our everyday lives would not be impacted. Instead, it would remove software glitches and crashes in technical systems. But a long-term impact will begin. By 2100, clocks will be ahead of the Earth by 54 seconds. In 2,000 years, there would be a huge gap between Earth's movement and our clocks. Sunset and sunrise will be significantly different compared to the body's natural rhythm.