Royal Collection Trust staff will spend more than 40 hours adjusting clocks at the Queen’s official residences. This includes 600 timepieces at Buckingham Palace, 450 at Windsor Castle and 50 at the Palace of Holyroodhouse.
Clocks go back an hour in the early hours of Sunday when the UK switches to Greenwich Mean Time.
A team of horological conservators will be kept busy through the weekend changing the clocks.
The Royal Collection contains historic clocks reflecting mechanical innovation over the centuries and the tastes of successive monarchs.
Many are on display to visitors at Windsor and Holyroodhouse.
Among the timepieces are musical clocks, astronomical clocks, miniature clocks and turret clocks.
Fjodor van den Broek is a horological conservator at the Queen’s Berkshire residence, where she stayed with Prince Philip during the coronavirus lockdown.
He expects to spend 16 hours this weekend changing the clocks on the Windsor estate.
Mr van den Broek told the BBC: “It’s just myself, and I have one colleague at Buckingham Palace who changes all the clocks there.”
Incredible attention to detail is needed as the clocks in the royal kitchens are five minutes ahead to ensure food arrives on time.
Mr van den Broek said: “People are still amazed that at Windsor Castle and Buckingham Palace there is a small time zone in the kitchens, where the clocks are always five minutes fast.
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“This is so that the food arrives on time… it’s a constant reminder that this is important.”
Mr van den Broek’s job includes spending one day a week winding up the mechanical clocks to keep their pendulums swinging.
His duties also include servicing and repairing clocks.
He said: “I check all the clocks in the state apartments before the public arrive to make sure they’re on time.
“Most of the clocks are quite accurate but every now and then, for no reason, they will suddenly start losing or gaining time – something which I’ve just started calling ‘life’.
“So I do have to keep a constant eye on them.”
The Queen, 94, returned to Windsor Castle on October 6 after her summer break in Balmoral.
The Duke of Edinburgh, 99, is at his Wood Farm cottage on the Sandringham estate in Norfolk.