The pips are 90 . .
This week saw the BBC's time pips turn 90 - they were first broadcast on 5 February 1924.
The 6 beeps were devised by John Reith, Head of the BBC, and Frank Watson Dyson, Astronomer Royal. They were controlled by 2 mechanical clocks at the Royal Greenwich Observatory - hence their official name, the 'Greenwich Time Signal'.
One difference back then was that the pips were all of uniform length - there was no elongated beep to round off the signal; that materialised in 1972.
Nowadays, the pips are broadcast most often on BBC Radio 4 and World Service, but also occasionally on BBC Radio 2 - and they are also mixed into the theme tune for many BBC news programmes.
Interestingly, the pips are tightly regulated and can never be broadcast as a sound effect - plays and comedies featuring fictional news programmes must find creative ways around the rule.
For practical purposes in setting one's watch, the pips on analogue radio can be considered accurate. Those via digital broadcasts - digital audio broadcasting (DAB) on radio or digital terrestrial television (DTT) - have a latency which makes them typically 5 secs late. Those via web-based radio are even later.
For much greater precision (typically tens of nanoseconds), one should use the likes of GNSS or eLoran - or MSF transmitting on 60kHz.
Details from the BBC links below . .