Rolex Datejust

Quartz watch:
The quartz oscillator replaces the balance wheel in the mechanical watch and uses its accurate high-speed oscillation timing to achieve high accuracy.
The monthly error is within 15 seconds (Swiss standard), and the annual error of some precision movements can be within a few seconds.

Mechanical watch:
The internal mechanical device is relied upon to control the watch to run at a constant speed and accurately. Errors occur due to the influence of gravity, environment and temperature.
There are slight differences depending on the movement model and manufacturing quality. Under normal circumstances, the daily error is within 30 seconds, and the error of some higher-precision movements (such as the Observatory series) can be controlled to about 10 seconds.