The four faces of Big Ben will return to Greenwich Mean Time (GMT) this weekend for the first time in five years.
British Summer Time (BST) officially ends at 2am on Sunday, and clocks go back one hour, giving people an extra hour in bed or an extra hour to party.
The Great Clock in the Elizabeth Tower, better known by the name of its bell, Big Ben, will be changed in the early hours of Sunday morning.
Commons spokesman Sir Lindsay Hoyle said the clock change would “herald a new beginning” for the landmark at the north end of the Houses of Parliament.
Parliament’s clockwork team will need a total of 24 hours over the weekend to ensure the estate’s 2,000 clocks are changed in time for the clocks to go back.
The Elizabeth Tower, clock and bell mechanism have been covered in scaffolding for the past five years as they undergo the most significant repair and conservation work in their 160-year history.
Hoyle said: “While the rest of us are holed up in our beds, our very own Father Time (clock) Ian Westworth and the team will be walking 8 miles changing our parliamentary clocks, including our favorite, the Great Clock of Westminster, better known as Big Ben.
“For the first time in five years they will be working with the clock’s completed original Victorian movement, making it an important final moment in the conservation of this magnificent timepiece.”
It will be the first time the clock has returned to GMT since it was restored and installed in the tower earlier this year.
People will only know that Big Ben is changing to GMT when the lights go out on all four faces of the sign at 10pm on Saturday.
Parliamentary clock mechanic Alex Jeffrey said: “This is so that people looking up don’t wonder why the hands are spinning and get confused.
“Under darkness, we effectively stop the clock and keep it going for two hours, only restarting it at midnight and turning the lights on the dial back on at 2am when it’s officially GMT.”
The clock was designed and installed in 1859, with the aim of creating the most accurate public clock in the world.
When the black paint on the dials was removed during repair work last year, it was discovered that it was originally painted in a color known as Prussian blue.