The last minute on June 30 this year will last 61 seconds, which is a phenomenon explained by the uneven rotation of the Earth.
The procedure of adding one second to match the two time scales, natural and atomic, is facing increasing criticism and can be expected to be abandoned in the near future.
In all countries of the world, on the night between June 30 and July 1, in "Coordinated Universal Time" (UTC), the minute between 23:59 and 00:00 will last one second longer than usual.
Although ordinary mortals will not even notice this "extra second", large satellite navigation systems as well as synchronization systems of large computer networks will have to take strict account of this change, Daniel Gambis, director of the Earth Rotation Service, explained to AFP.
With the added second, we align two time scales, Universal Time (UT), based on the Earth's rotation and its position relative to space bodies, and International Atomic Time (TAI), established in 1971.
When Universal Coordinated Time was established by international convention in 1972, it was agreed that the difference between the two time scales cannot be greater than 0,9 seconds.
Since that year in 1972, 26 seconds have been added (including the one on June 30). One second was last added in June 2012, and before that in June 2008.
"The earth spins on its axis while atomic clocks are deathly disciplined," Gambis stated.
In the long term, due to the gravitational influence of the Moon and Sun, which affect the tides, the blue planet tends to slow down its motion. It is also sensitive to atmospheric movements, changes in the ice cover, earthquakes, so one day does not last exactly 24 hours.
Planet Earth takes a little over 86.400 seconds to complete a 360-degree revolution, or turn one circle around its axis.
Atomic clocks, on the other hand, are extremely precise, so that a difference of one second could occur with them only every 300 million years.
Currently, more than 400 atomic clocks in the world enable the International Bureau of Weights and Measures in the French city of Sèvres to calculate Universal Coordinated Time.
Certain countries, such as France and the US, are against adding this one second, considering it to complicate matters unnecessarily, while others, such as Great Britain, are in favor of keeping it.
A debate on that topic will be held within the International Telecommunication Union next November in order to decide on a scientific level whether to abolish the disputed second or not.
Bonus video:
