Suddenly your wristwatch is running 10 minutes fast. Or 10 minutes slow. Or, inexplicably, it stops entirely.

What happened? It could be your smartphone’s fault.

At the risk of pitting your personal gadgets against one another, in a kind of crazy electronic “Toy Story” scenario, the high tech tools we have come to rely on aren’t entirely compatible with traditional timepieces. In close contact, their internal magnets can dramatically affect a watch’s accuracy.

And while magnetization isn’t a new problem for watches, the things that can cause it are proliferating.

“Today we have the highest level of magnetic fields around us,” said Stefan Ihnen, associate director of technics, research and development at IWC Schaffhausen. His list of culprits includes not only smartphones and tablets, but also handbags, which frequently have magnets in their clasps.

And there are other everyday offenders, including hair dryers, the closures on some necklaces and bracelets and that magnet of a plastic basket of oranges from the family’s last trip to Florida that’s now on the refrigerator door.

Even more intense is the magnetic field around machines like medical MRIs and airport security scanners. “Everything’s got a strong magnet these days, even things like home audio, hi-fis, the loudspeakers on your computer,” said Justin Koullapis, a co-owner of Watch Club, a boutique in London’s Mayfair neighborhood, and the technical editor of The Horological Journal, the British Horological Institute’s monthly publication.

Magnetization is a particular problem for mechanical watches, as it can cause some of the essential running parts, like the balance wheel and hairspring, to stick together and influence timekeeping accuracy. But quartz watches can be affected, too, as they often have steel hands that are sensitive to magnets.

Inadvertently magnetizing your watch is easy: Placing it on top of your phone on a nightstand can do it, or simply having your wrist too close to someone whose purse has a particularly strong magnet clasp.

Proximity increases the possibility of magnetization. “It would have to be really close,” Mr. Koullapis said. “The farther you move away from a magnetic source, the effect drops away very rapidly.” So going through airport security may not affect your watch, for example, but having a hand-held screener waved over it could produce different results.

Many wearers initially don’t understand what has happened to their timepieces. “They don’t typically know that it’s magnetized unless it’s happened to them before,” said Ruediger Albers, president of American operations for Wempe, the watch and jewelry retailer headquartered in Hamburg, Germany. “They just report the same symptoms: that the watch, all of a sudden out of nowhere, without being dropped or impacted, either gains time, runs slow or stops. All three are possible.”

Watch magnetization is easy to diagnose at home: Place your watch near a compass. If the compass needle moves, your watch has been magnetized.

But don’t worry too much. The condition isn’t permanent and it’s simple to remedy with the right equipment.

Most watch repair facilities have a demagnetizing machine, which takes just a few minutes to remove the watch’s magnetic field by quickly alternating its electrical current. Mr. Albers said his staff solves the problem with a three-step process that includes, at the end, checking the timepiece with what he called a “watch EKG” to ensure it has returned to proper operation. The service, he said, is offered free at Wempe’s Manhattan boutique, although the store is temporarily closed because of the pandemic lockdown.

Demagnetizing machines for home use are readily available online and, with many options priced at less than $20, comparatively inexpensive.

Decades ago, watch brands, aware of the recurrent problem, began to offer timepieces designed to resist magnetic fields.

One of the best known is Rolex’s Oyster Perpetual Milgauss, introduced in 1956; an updated version is offered by the company. The watch is said to resist as much as 1,000 gauss of magnetism (the name combines a variation of mille, the French word for thousand, and gauss, a magnetization measurement). That’s ample protection from everyday items like a typical hair dryer, but a fraction of the protection needed against a modern MRI machine, which can emit a magnetic field of 30,000 gauss.

The Swiss brand Alpina has introduced several antimagnetic watches since the 1930s. Its most recent option, the Alpiner 4, appeared in 2016. It promises to resist exposure to slightly more than 60 gauss of magnetism, the magnetic field that would be produced by about 40 stereo speakers booming in proximity. (The brand actually calculates magnetic strength with an alternate unit of measurement, called amperes per meter. The choice of which system to use is, according to Mr. Koullapis, simply “a question of style.”)

IWC and Jaeger-LeCoultre have offered antimagnetic watches since the World War II era, marketed mostly at pilots; Omega introduced the Railmaster, designed to withstand 1,000 gauss of magnetism, in 1957.

IWC’s latest series of Top Gun pilot watches, introduced last year, is resistant to more than 50,000 amperes per meter, Mr. Ihnen said. That’s far more than 600 gauss. He added that the brand is planning over the next few years to introduce more watches with that very high level of magnetic resistance, presumably to withstand today’s all-but-unavoidable onslaught of items with strong magnets.

Brands typically make watches antimagnetic in two ways: using materials like silicon, which don’t conduct a magnetic charge, or enclosing the movement in a soft-metal case.

Many brands have developed their own versions of antimagnetic materials — mostly silicon alloys, like, for example, Silinvar, created in collaboration by Rolex, Patek Philippe, the Swatch Group (which owns Omega) and the Swiss research group CSEM.

A soft-metal case — like a Faraday cage, which conducts magnetism away from the movement — adds bulk to a timepiece so is more suitable for a chunky sports watch than a thinline style.

“If you wanted a very small dress watch it’s harder, but for the sort of military-rooted watches we’re trying to make, it’s absolutely fine,” said Nick English, co-founder of the British watch brand Bremont. His brand’s Martin-Baker collection features movements that are suspended in rubber shells and surrounded by Faraday cages.

Such watches have to have solid cases. “If you have a Faraday cage, you will have a back where you can’t show your movement,” said Raynald Aeschlimann, Omega’s president and chief executive. In 2013, the brand introduced an antimagnetic version of its Seamaster Aqua Terra, which did not cage its movement but still promised to resist magnetization up to 15,000 gauss. A few years earlier, when the company had begun developing the timepiece, it noticed that as much as 40 percent of all its service requests concerned magnetization.

In 2015, the brand introduced an eight-step testing process for several functions, including resistance to magnetism. Many of its watches are subjected to that test, now accredited by the Federal Institute of Metrology in Switzerland, and are marketed as antimagnetic.

In February, the International Organization for Standardization, an independent group based in Switzerland that issues guidelines on a broad range of products, published a report on watch magnetization, something it first examined in 1973. It did not call for a change in its original standard — watches can be described as antimagnetic if they resist 4,800 amperes per meter of direct contact, but it did add a new category of enhanced magnetic resistance at 16,000 amperes per meter.

It’s just one more indication that the exposure of watches to magnetic fields looks likely to increase in our electronic-fueled environment.

“It’s a phenomenon of our cosmos,” Mr. Koullapis said. “Don’t blame the watch.”