Amzar File

Year 2008 earns one more second due to slower Earth rotation

BEIJING, Dec. 22 -- The year 2008 will be one second longer as the global time service system will be adding a leap second at the end of the year to keep it synchronized with the rotation of the earth, the China's National Time Service Center said Monday.

This will be the 24th time adjustment since the International Earth Rotation Service (IERS) called for the first leap second in 1971.

The leap second will come at 12:00 p.m. by Greenwich Mean Time (GMT) on Dec. 31.

For China, which uses the Beijing Time, eight hours ahead of GMT, the leap second will come at 7:59 a.m. on January 1, according to National Time Service Center based in Xi'an, capital of northwest Shaanxi Province.

The time people read from ordinary timepieces is determined by the rotation of the Earth and its celestial position, or universal time, which is counted 0 hour at midnight.

However, the Earth rotates in different speeds in different years, as it is affected by the moon's gravity, said Dou Zhong, a senior researcher at the center.

The international scientific community has relied on atomic clocks in since 1958 to accurately measure time based on atomic resonance frequency.

The atomic time that the IERS releases is calculated from the readings of more than 200 atomic clocks located in metrology institutes in about 30 countries, including China.

Although non-binding, countries throughout the world accept coordinated universal time announced every few years. The IERS rules that any time difference bigger than 0.9 second necessitates a one leap second in universal time.

In a world that is increasingly more interconnected, Dou said, any refusal to the coordination in particular countries might lead lapse or even collapse in communication, aerospace, finance and transportation.

Since the introduction of atomic time, the Earth's rotation has gained 33 seconds. The last leap second occurred before 2006.