The BT Speaking Clock has been ticking 24-hours a day, seven days a week since 24th July 1936.
(If you work it out, this is around 67 years, which is more than 24,000 days, more than 586,000 hours or 35 million minutes! And that, I think you will agree, is a long time. (Oh, and if you're reading this beyond 2005, it's been even longer.))
