self setting clock

[camioneur]

We've just bought a bedside alarm clock (electric) without radio for �9.99 from Argos. When we switched it on for the first time it set itself to the right time! How does that work then?

[Buenchico]

Radio-controlled clocks pick up the signal transmitted from the atomic clock at Rugby. The system is accurate to within one second every 300,000 years.

http://www.bbc.co.uk/dna/h2g2/A850141

Chris

[heathfield]

These cheap radio-controlled clocks are brill. I have several, and it's a joy to see them reset themselves after a mains power drop-out! Or automatically correct for Summer Time!

But most are manufactured in Germany and therefore use the atomic clock in Braunschweig. Signals are transmitted on Very Low Frequency (77.5kHz) from a radio station some 25km SE of Frankfurt-on-Main, and have a range of approximately 1500km.

[sarnieken]

Some clock radios use RDS to receive their times. These are often cheaper then the atomic clock ones and are equally as accurate, providing the right time is being transmitted. :)