What is meant by "coming apart from" in this context?
An alternative rule would be to require that all clocks, everywhere on Earth, keep time with Greenwich Mean Time. We don’t usually use that alternative rule, because it’s inconvenient for noon to occur in the middle of the night in some parts of the world, but that doesn’t make it wrong, just less useful. (Indeed, in some circumstances—military operations, for instance—it turns out to be more useful, with the benefits of a shared time outweighing the costs of that time coming apart from Sun and Moon.)
Source: Philosophy of Physics by David Wallace
