This is a mechanical watch powered by a spring.
To use it from a stopped state, turn the crown 20 turns by hand to wind up the spring before starting the watch.
Although the accuracy of quartz watches is measured in differences over months or years, in mechanical watches it is measured in differences per day (i.e., the amount the watch speeds up or slows down in a single day).
Additionally, mechanical watches are subtly affected by the conditions in which they are used (e.g., duration worn, temperature, arm movement, the amount wound, etc.) ; thus, the amount of error is not constant.
When affected by a strong magnetism from outside, the mechanical watch may lose/gain time. The parts of the watch may become magnetized depending on the extent of the effect. In such a case, consult the retailer from whom the watch was purchased since the watch requires repair including demagnetizing.