How UK Time Is Kept: Atomic Clocks and the MSF Signal
Official UK time comes from atomic clocks at the National Physical Laboratory in Teddington, south-west London.
The national timescale
The National Physical Laboratory, NPL, maintains the UK's national time scale, called UTC(NPL), using a group of atomic clocks including a caesium fountain clock, which is accurate to a second in tens of millions of years.
How the time reaches you
NPL's time signal, called MSF, is broadcast from Anthorn in Cumbria on a 60 kHz radio frequency. Radio-controlled clocks and watches receive it and set themselves, which is why they change on the right day without help.
The BT speaking clock, started in 1936, and network time services provide the same national time by phone and internet.
Frequently asked questions
Where is the MSF time signal broadcast from?
From Anthorn in Cumbria, on 60 kHz. It is operated for the National Physical Laboratory.
Clock change guides
- What Is Daylight Saving Time (DST)? A Plain-English GuideWhat daylight saving time is, how it works in the UK, Europe and the US, why it exists, its history, who uses it and the argument over scrapping it.
- Why Do the Clocks Go Back in October? The Real ReasonThe clocks go back in autumn to return the UK to GMT, so winter mornings are lighter. The history, the rule, what time it happens and what changes for you.
- When Do the Clocks Go Forward Again After Going Back?When the UK clocks go forward again after the autumn change, how long the UK stays on GMT, when evenings get lighter and how to remember to reset your clocks.