Northern Europe, the fourteenth century

For a thousand years the monastic hours are elastic. Prime at dawn, vespers at dusk, and the divisions between them stretch in summer and contract in winter, because the day is a quantity of light and the light is not the same in June as in December. A monk in Nuremberg and a monk in Palermo keep the same office at genuinely different lengths and neither is in error.

Then somebody in a monastery — the name is not recorded, which is itself the point — solves the problem of the verge escapement, and a weight on a rope can be made to fall in equal intervals forever.

The hours go rigid. An hour is now a length, not a portion. Sixty of them, identical, indifferent to the season, indifferent to the latitude, indifferent to whether anything is happening.

Within two generations the mechanism has left the cloister for the market square, because merchants have discovered that an identical hour can be bought and sold and a portion of daylight cannot. Within four, the word punctual has acquired its modern sense. Within six there is a machine small enough to carry, and being late has become a defect of character rather than a fact about a road.

Nobody experiences this as an imposition. Everybody experiences it as the discovery of what time had been all along.

The clock did not measure the day. It replaced it, and then the day was assessed against it for accuracy, and where the day disagreed the day was corrected. This is the whole operation, performed once, in wood and iron, six hundred years before anyone had a word for it.