WUHAN -- Scientists in Central China's Hubei province said they have assembled the country's first optical clock, which measures time more precisely than traditional atomic timekeepers.

The optical clock, based on a single calcium ion, can remain accurate within one second for more than 10 million years, said Gao Kelin, a researcher at the Hubei Academy of Sciences.

Gao said his group uses electric and magnetic fields to "trap" a calcium ion for more than 15 days, allowing researchers to pinpoint the passage of time by tracking the ion's atomic movement.

"Unlike microwave clocks, which track atomic movement in the microwave range, optical clocks observe the optical range, which can reduce uncertainty by 100 to 1,000 times," Gao said.

The breakthrough has made China the seventh country in the world to build such a clock following the US, Germany, the UK, Canada, Austria and Japan, Gao said.

Atomic clocks, including microwave and optical clocks, can be used to provide extremely precise measurements of time that are used in fields ranging from telecommunications to the manufacture of precision instruments.