Tomorrow time is pulled back by a second

Time experts around the world will add one second at the last minute of June 30.

Sun time is the time scale that 12 o'clock noon is when the sun is in the highest position in the sky. It involves the rotation of the earth around the axis and is expressed in GMT and UTC hours.

The globe rotates a circle around its axis in 86,400 seconds. However, the tilting position of the earth on the axis, the gravitational pull of the moon and the sun causes its rotation time to decrease by a few percent per year. The consequence is that the solar time is slower than the International Atomic Time (TAI) - measured by the oscillation of electromagnetic waves emitted by atoms or molecules moving from one energy level to another other energy.

Before June 30, the scientists added a leap of 24 times since 1972.

Leaving the error between the solar time and the atomic time does not increase gradually, every few years the scientists add another second (called leap seconds) to the time the sun leaves it by atomic time. This measure has been implemented since 1972. Earth Rotation Monitoring Agency and Reference Systems determine the time of leap seconds. Usually leap seconds are added on December 31 or June 30. This is the 25th time humans have added leap seconds to the length of a day.

'Today time is defined, built and measured by atomic clocks. The atomic time is more stable than the astronomical time, so it allows people on earth to see the same time on the clock , 'Noel Dimarcq, director of the space reference system - time of the Paris Observatory, told AFP.

Several hundred atomic clocks across the planet are in charge of maintaining the International Atomic Time. They measure vibrations in cesium atoms and can divide one second into 10 billion parts.

'With that precision, every 300 million years of a new atomic clock slows a second,' Dimarcq said.