Age: 127, or older if you like.
Why older? Greenwich Mean Time (GMT) was adapted for the British railway timetable in 1847, but wasn't adopted as an international standard until decades later.
Fascinating. What is it? The time of day at the line of zero longitude, which just happens to run right through the Greenwich Observatory in London.
How convenient. And what luck! Actually, it was established quite intentionally at the International Meridian Conference of 1884. Everyone agreed the line had to be somewhere, but the French wanted it to run through Paris. They abstained from voting and didn't adopt GMT until 1911.
Cripes. How long can you bear a grudge for? You'd be surprised: 127 years later, the French-based International Bureau of Weights and Measures is pressing for a new system based on atomic clocks, rather than the Earth's rotation. In terms of timekeeping, GMT would cease to mean anything.
That's crazy. It makes no sense. It's because the Earth's rotation is irregular, and generally slowing. The resulting inaccuracies can potentially cause problems for modern telecommunications technologies.
OK, that does make a lot of sense. Why should we be sentimental about GMT? If we ignore the Earth's rotation, time will get out of sync with the cycle of night and day. "Eventually our midnight would happen at noon," says science minister David Willetts.
When? In 36,000 years.
Right. Of course, in 1972 we did more or less abandon GMT in favour of Co-ordinated Universal Time (UTC), which relies on atomic clocks but is corrected by adding leap seconds to keep things in sync. The new system will just employ fewer and larger corrections.
Will it still be morning when I wake up? Yes.
Will I be able to record Downton Abbey without cutting off the beginning? Yes.
In that case, I'm going to ask you to stop bothering me. Sorry.
Do say: "And anyway it was the British who invented the atomic clock."
Don't say: "I propose that, for economic reasons, we move GMT to Salford."
