Japan Institute to Use Domestic Commercial Optical Lattice Clock to Set Japan Standard Time

The Yomiuri Shimbun

7:00 JST, January 28, 2026

An optical lattice clock, which is only off by one second every 10 billion years, will be used to decide Japan Standard Time, The Yomiuri Shimbun has learned.

The National Institute of Information and Communications Technology (NICT), a state-run research and development agency that decides Japan Standard Time, will introduce an optical lattice clock domestically produced for the commercial use by the end of this year at the earliest. The clock will be used to correct errors in the standard time.

Optical lattice clocks were originally invented in Japan. The clocks measure time by vibrating a large number of atoms trapped in laser lattices. They are regarded as the world’s most accurate, off by only one second every 10 billion years.

Prof. Hidetoshi Katori of the University of Tokyo, who devised the principle of the mechanism, is considered a candidate for a Nobel Prize.

The clock to be used by the institute was developed by Shimadzu Corp., based in Kyoto.

Maintaining accurate time measurement is essential for information communications and financial transactions that use the internet. Currently, Japan Standard Time is decided mainly by cesium atomic clocks, as international organizations use that kind of clock to define the length of one second.

However, cesium clocks experience lags of 20 nanoseconds about every month. One nanosecond is 1 billionth of a second.

Therefore, the NICT will correct the time lag with the optical lattice clock, which is more than 100 times more accurate than a cesium atomic clock. This will reduce the time lag to less than a quarter of its current state.

The NICT will use the world’s first commercial-purpose optical lattice clock — named Aetherclock, it was jointly developed by Katori, Shimadzu Corp. and other partners. The clock is about one meter high and about one meter wide, and weighs about 200 kilograms.

Since 2012, the institute has corrected Japan Standard Time with an optical lattice clock that it developed on its own. It will introduce the commercial-purpose clock developed by Shimadzu at a price of about ¥400 million.

The NICT will strengthen its backup system in case of mechanical trouble by utilizing both clocks, so it can always decide and provide Japan Standard Time with extreme accuracy.

Optical lattice clocks are expected to be used for a wide range of purposes.

According to Albert Einstein’s general theory of relativity, time passes more slowly in lower places that are more strongly affected by gravity than in high places. Optical lattice clocks can measure even very minimal time gaps that are caused by differences in altitudes. Research is actively conducted to apply the technology to observing crustal movements and land surveys.

“By correcting Japan Standard Time and other efforts, I want to show the world that this technology can have practical applications,” said Tetsuya Ido, director of the Space-Time Standards Laboratory of the NICT.

Japan Standard Time is nine hours earlier than the Coordinated Universal Time, which is decided by the International Bureau of Weights and Measures in France every month. Japan Standard Time is based on the time at 135 degrees east longitude, which passes through Akashi in Hyogo Prefecture.