About magnetism

Analog Quartz watches and Springdrive watches are more affected by magnetism than Mechanical watches.

In fact, Analog Quartz watches move their watch hands using a stepping motor magnet inside.

So if they receive outside magnetism, the accuracy is worse.

With regard to Springdrive watches, they use a magnetic brake to control the accuracy. So again, outside magnetism affect their
accuracy.

Compared to above two watches, Mechanical watches are tough against magnetism.
However, they are also affected by magnetism.
If a hair spring is magnetic, it will not vibrate accurately. Then accuracy will be worse.

On the contrary, Digital Quarts watches are not affected by magnetic.
Because they don't use a stepping motor.

Source: page 22,  SEIKO.ALBA.WIRD Watch Catalog 2007