When the clock strikes 5.33pm today it will pass by without fanfare for most radio stations, but on the BBC it will mark a seminal moment.
The Corporation is celebrating 90 years of broadcasting, and will mark the occasion just after 5.30pm this evening with a one-off composition played across every BBC radio station.
The special composition, created by Blur frontman Damon Albarn, will be heard by millions and will be the first simultaneous radio broadcast since 1922, the year the BBC was established.
For BBC listeners, it will be a powerful display of how far the Corporation has come in the 90 years since its first daily radio service, codenamed 2LO, which hit the airwaves on November 14 1922.
Having been founded with the ethos 'to inform, educate and entertain', 2Lo was broadcast for the first time from the top of the Selfridges building on London's Oxford Street.
The first news bulletin, just like current affairs programmes today, featured a range of topics - although in 1922 they ranged from details of Old Bailey sessions, fog in London, and 'the latest billiards scores'.
News bulletins were even read twice - once quickly and once slowly - by Director of Programmes Arthur Burrows.
A year later saw another iconic BBC moment, as they released the first ever Radio Times, the enduring TV listings guide which went on to become one of Britain's best-selling magazines.
In 1924, the BBC would broadcast the words of a monarch for the first time when George V was heard on the wireless service.
The landmark broadcast was heard by millions and brought traffic in central London to a standstill as crowds gathered to listen on loud speakers.
Another first in 1932 saw George V broadcast his Christmas message, which had been scripted by Rudyard Kipling.
Three years on, the Corporation celebrated the King's silver jubilee, before being the first to broadcast a royal funeral when the monarch passed away in 1936.
Years later when war swept across Europe, Prime Minister Neville Chamberlain would take to the BBC airwaves to declare the UK at war with Germany.
Decades on it has grown into one of the world's biggest media organisations, and despite the controversy of recent weeks remains one of Britain's most trusted news outlets.
The BBC hope tonight's composition will have a huge reach - officials say it could be heard by as many as 80 million people, tuning in to 55 stations.
The piece, '2LO Calling', starts with Big Ben's famous chimes, and features the first ever broadcast from the 2LO transmitter.
The three-minute piece also features messages from listeners around the world along with the sound of the blackbird and skylark, as well as the unmissable BBC pips.
Albarn, 44, said: "There is a special musicality to some of the vocal messages, which I tried to preserve.
"Added to that, I got to do what I've always wanted - to play along with the pips."
The broadcast at 17:33 GMT will be hosted by BBC Radio 2's Simon Mayo from London's Science Museum.
Tim Boon, head of research and public history at the Science Museum, said: "The first broadcast by the 2LO 90 years ago marked the moment when radio moved from the realm of the 'amateur enthusiast' to the first proper public broadcasting service in Britain.
"This exhibition takes visitors back to a time when everything, from the technology to the content of the programmes was still new."