National Physical Laboratory

Time & Frequency Time & Frequency

Home of the nation’s atomic time scale, NPL is the focus for time and frequency measurements and research in the UK.


The Time & Frequency Group is responsible for operating the national time scale UTC(NPL) and disseminating time throughout the UK. Our caesium fountain primary frequency standard measures the SI second at the highest accuracy, and we contribute to the generation of the world's reference time scale UTC. We also maintain and disseminate another of the seven base SI units: the metre.

We carry out a broad programme of research in time and frequency metrology. A major activity is the development and characterisation of a new generation of optical atomic clocks based on laser-cooled trapped ions and atoms, which may lead to a future redefinition of the SI second. Potential applications of these clocks range from improved satellite navigation systems to sensitive tests of fundamental physical theories.

Other areas of current research include the development of compact and user-friendly frequency standards for industrial applications and unique algorithms for processing clock data to generate the most stable reference time scales achievable.

National Time Scale

NPL's Peter Whibberley discusses the National Time Scale

What is Time?

Here at NPL, atomic clocks keep UK national, and international time ticking. Our scientists are developing ways to measure time ever more accurately.

Find out more


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