National Physical Laboratory

What is Time?

Here at NPL, atomic clocks keep UK national, and international time ticking. In 2015 we celebrated 60 years of the Atomic Clock; in 1955 Louis Essen and Jack Parry designed and built the world's first successful atomic clock at NPL in Teddington, transforming the way we measure and use time.

Time Measurement

The World Time System

How do countries all keep the same time? Find out about the different time systems and how they all link together.

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How do atomic clocks work?

Atomic clocks provide the basis for all precision timekeeping. Discover the science and technology behind the atomic clock.

More on Atomic Clocks

Why do we need accurate time?

The atomic clocks at NPL provide the most accurate time available. Find out more about why we need accurate timekeeping systems.

More on accurate time

MSF radio time signal

The UK time scale

Microwave frequencies provide the standard time for the whole of the UK, and are broadcast via radio signals, telephone lines and the internet.

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Synchronise with NPL's atomic clock

You can set up your computer to synchronise with NPL's atomic clock.

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Timekeeping is a basic part of everyday life, from checking your watch to using satellite navigation.

NPL's research is at the forefront of new time technologies, while our current atomic clock system keeps time for the whole of the UK.

NPL has a long history of time research, not least of which being that the first caesium atomic clock was built here.

The current atomic clock system at NPL is the basis of UK time, and the cutting-edge research being carried out is working to improve timekeeping accuracy even further.

Useful links


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Find out more about, NPLTime®, a resilient, traceable and certified time distribution service for the financial sector that completely eliminates reliance on GPS.

NPL and Time

The world's first caesium atomic clock

The world's first caesium atomic clock was developed here at NPL.

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NPL and Coordinated Universal Time

Find out more about NPL's role in the worldwide time system.

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Time Research

Case studies

Discover how past and current research at NPL is helping to shape future technologies.

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Time research highlights

Find out more about the research currently being carried out by NPL's Time and Frequency research group.

Visit NPL's Time research pages


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