Six days on one movement

A movement leaves assembly running. That is not the same as running well. Rate varies with position, because gravity pulls on the balance differently when the watch is dial up, dial down, or resting on any of its four crown orientations.

The six positions

Dial up, dial down, crown down, crown left, crown up, crown right. Each is measured over a full day, because the errors that matter are the ones that accumulate. A movement that looks perfect over ten minutes can be several seconds out over twenty-four hours.

Why it cannot be rushed

Every adjustment changes every other reading. Moving the regulator to correct crown-down affects dial-up. Poising the balance to fix one position moves two more. The work converges rather than completes, and the person doing it decides when the spread across all six positions is small enough to stop.