Are watches/clocks affected by magnetism?

Pay attention to surrounding electrical appliances because time indicated on timepieces may become incorrect if they are affected by magnetism.

Many products in our environment generate magnetism, such as electrical appliances (speakers of audio equipment, etc.), mobile phones, magnetic necklaces, and magnets in furniture or bags. If your timepiece suddenly stops, or loses or gains time, it may be affected by magnetism. Magnetism resistant watches designed to minimize the effect of magnetism are commercially available.

Analog quartz timepieces and combination quartz timepieces

An analog quartz or combination quartz timepiece is equipped with a motor drive system that uses a magnet to move the hands. If the normal rotation of the motor is affected by strong magnetism from the outside, the timepiece may also stop, or lose or gain time. In such a case, the timepiece is not broken even if the displayed time is not correct. Therefore, its original accuracy may be restored if the timepiece is moved away from the magnetism source. You may use it again after setting the correct time.

Mechanical timepieces

Mechanical timepieces may also lose or gain time when affected by strong magnetism, though it is not as much as with quartz timepieces. Once a mechanical timepiece has been affected, magnetism remains in the movement even if it is moved away from the magnetism source. Accuracy problems may persist after a long time so it is necessary to demagnetize (repair) the timepiece. Contact the retailer from whom you purchased the watch for information about demagnetization.

Precautions when using your watch

Magnetic necklaces and mobile phones generate strong magnetic fields. When taking off your watch, do not place it near magnetic necklaces and mobile phones, or in a bag containing these objects.
Pay also attention to medical equipment as they sometimes generate extremely strong magnetism.

Magnetic resistance performance

Type	Magnetism resistance (in case of direct current magnetic field)	Explanation
Common timepiece	Up to 1,600 A/m (approx. 20 gauss)	The minimum magnetism resistance requirement for a watch. (For reference)
Type 1 antimagnetic watch (magnetic resistant watch)	Up to 4,800 A/m (approx. 60 gauss)	A magnetic resistant watch almost always maintains its performance when placed at 5 cm from magnetic field generating devices of everyday life.
Type 2 antimagnetic watch (super magnetic resistant watch)	Up to 16,000 A/m (approx. 200 gauss)	A super magnetic resistant watch almost always maintains its performance when placed at 1 cm from magnetic field generating devices of everyday life.
Diver's watch	Up to 4,800 A/m (approx. 60 gauss)	The magnetism resistance requirement for a diver's watch.

Type 1 and 2 requirements are defined in JIS B 7024 - Magnetic resistant watches, and diver's watch requirements in JIS B 7023 - Divers' watches - Classification and performance.
Generally, resistance of watches is indicated according to the old JIS B 7024 standard, but indications are now being changed for the current ISO standards.