A speaking clock is a live or recorded human voice service, usually accessed by telephone, that gives the correct time.
First mentioned in the book So Long, and Thanks for All the Fish, Ford Prefect uses the speaking clock to try and bankrupt a merchant by running up an incredibly long phone bill. He, with difficulty, rang the Speaking clock from the Pleiades, then left the ship he was hitchhiking on, leaving the clock running.
In the book Mostly Harmless, a more advanced version of the speaking clock is introduced when Arthur Dent and Random Dent are stranded on Lamuella. Random uses a speaking clock that is part of the technology implanted in her wrist to prove to Arthur that his watch is wrong.
- In the United Kingdom, the speaking clock can still be reached by dialling 123 or a similar number. Every ten seconds, a voice announces: "At the third stroke, the time from BT will be (hour) (minute) and (second) seconds."
- Speaking clock on Wikipedia