As the clocks went back this autumn, the horological conservator at Windsor Castle was busy changing more than 400 clocks from the Royal Collection Trust.
For those of us with smartphones and smartwatches, the change to Greenwich Mean Time last weekend happened automatically whilst we sleep. But for the hundreds of clocks in the Royal Collection at Windsor Castle, each one will needed to be changed by hand to ensure accurate timekeeping for visitors and residents.
Fjodor van den Broek is the current horological conservator of the 900-year-old royal castle.He spent about 16 hours over the weekend changing all 400 clocks on the Windsor estate, including about 250 in the castle itself, along with seven tower clocks.
"It's just myself, and I have one colleague at Buckingham Palace who changes all the clocks there," Fjodor told the BBC. For some clocks there is an extra time difference to take into account.
"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. "This is so that the food arrives on time... it's a constant reminder that this is important."
When he's not changing the time, Fjodor's job includes spending one full day a week winding up the mechanical clocks to keep their pendulums swinging. On a typical day of walking around the castle and winding clocks, the step counter on his watch will record about 16,000 steps.
"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 rest of his week is spent in his workshop servicing and repairing clocks, many of which are 200 to 300 years old.