British timekeeping has marked the end of an era with the switch to summer time in the early hours of Sunday.
The change at 0100 GMT was the last one to be signalled from Rugby, in Warwickshire, which has been the source of the time signal since 1927.
From 31 March, the long-wave signal, which helps keep the "pips" heard on BBC radio services accurate, will start to be broadcast from Anthorn, Cumbria.
The contract to transmit the signal is switching from BT to VT Communications.
Users of the signal, such as emergency services, banks and mobile phone networks, should not notice any change.
"The signal is already up and running and they are swapping between the two," said Fiona Auty of the National Physical Laboratory (NPL), which has responsibility for the time signal.
"So there are times when people are picking up the signal from Cumbria without even knowing it."
World clock
The national time signal is accurate to within 1,000th of a second of Co-ordinated Universal Time.
It is controlled by two caesium atomic clocks housed at the antenna in Rugby.
"They are typically accurate to tens of nanoseconds, or billionths of a second, over a day," said NPL's Dr Peter Whibberley.
These are kept in line by comparing them to GPS signals and a suite of reference clocks at NPL in Middlesex.
"That allows us to get a good measure of whether those clocks are changing - we can then apply an adjustment if necessary," said Dr Whibberley.
The master clocks at NPL are in turn kept in check by comparing them with measurements from atomic clocks around the world, a task co-ordinated by the Bureau International des Poids et Mesures (BIPM), near Paris.
Changing hands
The national time signal underpins many aspects of society.
"It's used incredibly heavily by police, the ambulance service, the fire brigade, in speed cameras on the road and clocks in train stations," said Miss Auty.
In addition, many home users have the relatively inexpensive receivers in clocks and some radios.
All receive the MSF 60 kHz signal, as it is known, currently transmitted from the Rugby Radio Station by BT under contract from NPL.
But the telecom company's contract has now expired, and responsibility for broadcasting the signal has changed hands to VT Communications.
Their mast, located on a Ministry of Defence site in Anthorn, on the west coast of Cumbria, will be easier to maintain than the older antenna in Rugby.
It will start broadcasting the national time signal around the clock from midnight on 31 March, one week after the switch to British Summer Time.
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