If a mechanical watch suddenly starts gaining much more time than usual, magnetism is one possible cause.
The balance wheel and hairspring form the oscillator that controls a mechanical watch’s rate. A magnetic field can disturb susceptible components. If coils of a traditional hairspring begin interacting, its effective length can shorten and the watch may run fast.
Common nearby sources include magnetic phone accessories, tablet covers, bag clasps, speakers, and some chargers. Modern movements may use silicon or special alloys to resist magnetism, but resistance varies by watch.
A sudden rate change is a clue, not a diagnosis. Shock, low amplitude, contamination, or a mechanical fault can also affect timekeeping. Compare the watch against a reliable time source over a full day, then have a watchmaker test it if the change persists.
Watcher Insight: demagnetizing is usually quick, but do not keep repeating it blindly. First remove the magnetic source; if the rate stays wrong, the watch needs diagnosis rather than another guess.
