Skip to main content

Changing the time on Big Ben

22 March 2021 (updated on 22 March 2021)

There is no description available for this image (ID: 152884)

Daylight Saving Time begins on the 28th March this year, with clocks going forward one hour, at 1 am. On the Parliamentary Estate, clock mechanics will be carrying out the task of adjusting the time on over 2,000 clocks across the Estate – including on the Elizabeth Tower.

What is happening inside the Elizabeth Tower for time change weekend?

Every year, the Palace of Westminster clock mechanics are responsible for changing the time on the Elizabeth Tower’s Great Clock when British Summer Time (BST) begins and Greenwich Mean Time (GMT) ends.

The process involves careful precision and split-second timing. Since 2017, an electric motor has been installed to drive the hands on the visible clock dial - while the original clock mechanism undergoes essential conservation work.

Parliament’s clock mechanics will disengage the electric motor driving the hands, set the hands to the new time and then re-engage the motor – ensuring the hands are rotating to the correct time again. 

Earth Hour

This weekend, time change will coincide with Earth Hour. All non-essential internal and external lights right across the Estate will be switched off, to raise awareness about the need for action on climate change.

On the Elizabeth Tower, the clock dial lights on the North side of the Tower will be dimmed for Earth Hour at 20:30 on 27th March and will remain off until time change has been completed.

The clock dial lights are to be switched on at 02:00 BST on the 28th March – revealing the correct time once again.

What about the rest of the clocks in Parliament?

Changing the time on the Elizabeth Tower clock face isn’t the only job for Parliament’s Clock Mechanics this weekend. There are over 2,000 other clocks throughout the Palace of Westminster and across the Parliamentary Estate that will also need to be adjusted to take account of the time change this Spring.

The Vulliamy 807 clock - which stands in the Members’ Staircase in the House of Commons - is the oldest clock on the Estate, pre-dating the fire of 1834.  It has stood in Parliament for almost 200 years and was supplied by Benjamin Lewis Vulliamy (1780 – 1854). It was ordered for the Members Waiting Room on the 30th Dec 1822 and is currently undergoing restoration work.  

Find out more about the history of the Great Clock here.

Big Ben: Changing the time on the Great Clock

Take a look at how the Great Clock's time was changed before the restoration started

Video thumbnail

Stay up to date

Elizabeth Tower sign up button.jpg

To receive the latest news about the Elizabeth Tower conservation project and Big Ben updates.

Sign up

Shop online for Big Ben gifts


Discover the range of Big Ben-related gifts and souvenirs available online.

Start shopping online