Our watchmakers explain
Magnetic fields can affect the proper functioning of the watch if they magnetize certain steel parts in the movement, especially the balance spring. The hairspring's coils can stick together and force the acceleration of the balance wheel.
The advice of our watchmakers
The watch runs ahead or behind, or even stops. The trick to diagnosing the problem yourself is to place your watch on a compass. If the compass needle loses its bearings, it means that your watch is magnetized.
Fortunately, the effects of magnetization are not irreversible, and not inherently dangerous.
However, it is advisable to have the watch demagnetized by a professional.
The best way to preserve your watch is to follow this simple rule: do not place your watch near any electronic device, such as your bedside table next to your cell phone.
This also applies to computers, tablets, magnets, speakers etc.