Why Your Watch Loses (or Gains) Time — and What You Can Do About It

Every watch is wrong, and none is wrong by the same amount. Even a very expensive one drifts. Understanding why makes it easier to judge whether your watch is behaving normally or needs attention.

Quartz watches: a tiny crystal with a temperature problem

A quartz watch uses a small tuning-fork-shaped crystal that vibrates 32,768 times per second when powered by the battery. A circuit counts those vibrations and moves the hands once per second.

The crystal's frequency changes slightly with temperature. It's designed to be most accurate at a certain temperature, and drifts if it gets much hotter or colder. Watches worn on the wrist stay fairly near 30 °C, which is one reason a quartz watch on your arm tends to keep steadier time than the same watch sitting in a cold car. Ageing of the crystal and a weakening battery also change the rate slowly over years.

Typical basic quartz watches are accurate to around 15 seconds a month. High-accuracy "thermocompensated" quartz models measure temperature and correct for it, and can hold about ten seconds a year.

Mechanical watches: many small forces at work

A mechanical watch runs on a mainspring, a set of gears and a balance wheel with a hairspring that swings back and forth like a pendulum. Lots of things affect its rate:

• Mainspring power. As the spring unwinds, the balance swings with a smaller amplitude, which can change the rate. That's why a watch can run slightly differently just after winding and just before it stops.
• Position. Gravity acts differently on the balance depending on whether the watch is lying flat, crown up or crown down. Watchmakers adjust the movement in several positions, and a real wrist rarely matches the workshop.
• Temperature. Metal expands and contracts. Modern alloys are much better than older ones, but the effect isn't zero.
• Magnetism. Steel parts, and especially the hairspring, can become magnetised by speakers, magnetic clasps, laptops and handbags. A magnetised watch often gains large amounts of time, sometimes minutes per day.
• Lubricant ageing. Oils thicken and dry over years, adding friction. A rate that slowly worsens over a few years often signals a need for service.
• Shocks. A hard knock can bend the hairspring or move the regulator.

What counts as normal?

The Swiss chronometer testing body COSC certifies movements that run between −4 and +6 seconds per day under lab conditions. Many good watches from well-known makers are certified tighter than that, and a lot of ordinary mechanical watches run at ±10 to ±30 seconds a day. On the wrist, expect to see more variation than the lab number, because real life is messier than a test bench.

What to do about it

1. Measure before you worry. Log the offset over a week using our calibration guide. A consistent rate isn't a fault.
2. Demagnetise if the rate jumped. If your watch suddenly gains a lot, ask a watchmaker to check for magnetism. It's a quick, inexpensive fix.
3. Adjust your habits. If it runs fast lying flat and slow crown-down, try resting it the way that offsets the error.
4. Service on a schedule. Manufacturers often recommend servicing mechanical watches every several years, though intervals vary. Ask your brand or an independent watchmaker.
5. Replace the battery in quartz watches before it is fully dead. A dying battery can cause erratic behaviour.
6. Consider radio-controlled or solar options if you value accuracy above all. Radio-controlled watches automatically correct themselves from time signals whenever they can receive one.

Your phone is not immune

Phones sync to networks regularly, which is why they look "perfect". A computer with no synchronisation can lose or gain a second or two a day, because its oscillator has the same kinds of small errors. If a device has been offline for a long time, its clock may drift noticeably.

The takeaway

A watch that gains or loses a few seconds a day isn't broken. It is a small machine reacting to temperature, movement and time. Measure it, learn its habits, and set it when you need to. If you travel, remember to adjust for the local offset, which you can look up for cities such as Paris, Dubai or Singapore.