Breezy Explainer: What is a leap second? Why are we scrapping it?

In order to maintain official clocks in sync with Earth’s rotation, the top metrology organization in the world has decided to stop adding “leap seconds” beginning in 2035. According to a story in Nature, the choice was made during a gathering of international representatives at the General Conference on Weights and Measures (CGPM) on Friday in Paris.

What is a leap second?

A day lasts 86,400 seconds in the time standard that we use, Coordinated Universal Time, or UTC (24 hours plus 60 minutes plus 60 seconds). A second on UTC is calculated by averaging signals from about 400 atomic clocks, which serves as the standard for international time zones. These clocks are so precise that they only miscalculate by a few seconds every 1,400,000 years.

The duration of a day, or solar time, which determines how long it takes for the Earth to circle around the Sun, is not necessarily 24 hours. It takes roughly 86,400.002 seconds, according to NASA. Therefore, leap seconds are inserted to keep UTC from drifting by around one minute every 90 years from solar time. Typically, a leap second is added on either June 30 or December 31.

Why was there a demand to stop this practice?

Three main arguments were made in favor of doing away with the synchronization technique.

1) It is difficult to forecast Earth’s orbit correctly. According to NASA, a variety of elements, chiefly the atmosphere on timescales less than a year, determine the length of the day; as a result, the shift cannot be pre-programmed. In addition, the Earth’s rotation has recently accelerated unusually.

2) According to experts, there is no compelling evidence that anything significant would change if the leap second were not added.

3) Tech firms must synchronize their digital systems globally. However, as the International Earth Rotation and Reference Systems Service in Frankfurt, Germany, normally only announces the leap year six months in advance, they cannot be pre-programmed into the software.

However, if the seconds are applied inconsistently across different systems, clocks may momentarily drift out of sync, potentially causing computer failure and opening up global financial markets to attack.

Among the tech firms that pushed for the elimination of leap seconds were Meta and Google.