If you use a radio-controlled watch in Western Europe, or observe an airport clock, the chances are that both are being calibrated from a laboratory in the north of Germany.

When European clocks were set back by one hour early Sunday morning, ending summer time, the change was largely automated using signals from a bank of atomic clocks in Braunschweig.

The 45-year-old man in charge of them, Ekkehard Peik, is head of the Time and Frequencies Department at the German Agency for Physics Technology.

"Our system of clocks has never stopped," he says proudly.

It sometimes happens that one clock fails and has to be replaced, but the set keeps going.

"An atomic clock only has a working life of five to 10 years," he said. The agency keeps a supply of replacement clocks at the ready and has staff on call all the time. Any malfunction is reported to the duty officer straight away.

Peik says switching from summer to winter time and back again has always been a routine matter, even if he does go into the laboratory in the middle of the night to supervise it each time.

"We've been in charge of it since 1980 and nothing has ever gone wrong," Peik said. When he is not minding the clocks, he plays the trombone. In his free time, so to speak. But he is always watching clocks, even on holiday.

"I was in the Netherlands and discovered that even the Dutch railways uses our radio signals to keep time," he said happily. The time signals are transmitted from big radio aerials and are used in much of Western Europe.

Peik's work has also brought an answer to a question that puzzles many railway travellers: why the second hands on station clocks sometimes zip regularly around the dial and then seem to hesitate slightly before pointing to 12.

"I could never understand it myself," he recalls.

"But now I know. Those clocks only receive our minute-by-minute signals, not our second-by-second signals. For most of the minute they are under their own control. The hesitation is when they come back into synch."

Peik has been studying atomic clocks since the days of his doctoral studies at universities and says time-keeping is not abstruse at all. "Time is something that most people feel and part of ordinary life," he said.

Not that he wastes any time himself.

His department is developing a new generation of atomic clocks that will be even more exact than those of today.