Daylight saving started in New Zealand in the early hours of Sunday morning, which led to a conversation in the work kitchen this morning about time.

Time is a construct, said the engineer among us, given importance by trains. He then whisked out of the room with his coffee, leaving the rest of us to discuss the concept.

He is, of course, quite correct. Once, everywhere in the known world took its time from the sun (translated into candle time or water time, but the reference point was the sun, as translated through some form of sun dial).

In fact, that’s still true today, since all the timekeeping in the English-speaking world relates back to Greenwich Mean Time, which is calculated from solar time — in fact, average solar midnight at Greenwich. (There’s a whole lot more history, but that’s enough for now.)

The thing is, up until the invention of railways, solar time was good enough. Even though clock technology improved, a clock was only as accurate as its reference point. Every village, every ship at sea, every point East to West across the map, calculated its own solar time. You could travel from the East of Kent to the West of Ireland, and have to put your watch back an hour.

Since the whole trip would take a couple of weeks, what did it matter? A few minutes between overnight stops made very little difference.

Then came the railways.

All of a sudden, exact times mattered. Not only were people travelling at four times the speed — and for longer each day; those controlling the railways needed to know when trains were going to be where, and know it precisely. It was a matter of life or death.

Here’s a fascinating map that shows how far out from solar time various parts of each time zone are. https://www.dailymail.co.uk/sciencetech/article-2572317/Are-YOU-living-sync-Amazing-map-reveals-manmade-timezones-countries-false-sense-sun-rises.html

You’ll see that in China, where all clocks are set to Beijing time, solar noon takes place at 3pm in the far west of the country.

On a related point, we think of a moment as a very brief fraction of time. This reflects our business, perhaps, because — for our ancestors — a moment was longer than a minute. How long? It depends. The word comes from a Latin root meaning movement, and the movement in question was that of a shadow on a sundial. A moment was the time it took the shadow to move between the two smallest marks. With 40 marks to an hour, at the equinoxes, a moment was 90 seconds in our time. A moment was longer in the summer, and shorter in the winter — something to tell your kids when you ask them to wait just a moment.