A watch is a regular beat and a way of counting it. In a mechanical watch the beat is a tiny wheel swinging back and forth on a spring, a few times a second. In a quartz watch it’s a sliver of crystal vibrating 32,768 times a second. That one difference explains most of what you’ll read below: a cheap quartz watch keeps better time than an expensive mechanical one, and the mechanical one is bought anyway, for the craft.
The short version
| Movement | Powered by | Typical accuracy | Upkeep |
|---|---|---|---|
| Hand-wound mechanical | A spring you wind with the crown | Often around ±10 to ±20 s a day | Wind daily; service every several years |
| Automatic mechanical | A spring wound by a weight that swings as you move | Same; chronometers −4 to +6 s a day | Runs down if not worn; service every several years |
| Quartz | A battery | Often ±15 s a month | New battery every few years |
| Solar quartz | Light, stored in a rechargeable cell | As quartz | Keep it out of a drawer |
| GPS or Bluetooth | Battery or solar | Corrects itself from satellites or your phone | Little |
| Smartwatch | A battery charged every day or few | Set from your phone | Charging |
Want to know how your own watch does? Our free watch accuracy checker measures it in seconds a day.
Mechanical: a spring and a swinging wheel
A mechanical watch stores energy in a coiled mainspring. The spring turns a train of gears, and an escapement lets those gears move forward one tiny step at a time, paced by the balance wheel, which swings back and forth on a hair-thin spring. Each swing releases one step. The ticking you hear is the escapement.
A hand-wound (or manual) watch is wound by turning the crown. An automatic watch adds a half-moon weight, the rotor, that spins as your wrist moves and winds the spring for you. Take an automatic off and it keeps going on its power reserve, often around 40 hours on an everyday watch and several days on some newer ones, then stops until you wear or wind it again.
Mechanical watches are sensitive to how they sit (face up, crown down and so on), to temperature, and to how fully wound they are. Many makers quote somewhere around ±10 to ±20 seconds a day for an ordinary automatic. A Swiss watch sold as a chronometer has passed the COSC test, 15 days in different positions and temperatures, with an average rate between −4 and +6 seconds a day.
Suddenly gaining minutes? It’s probably magnetised
If a mechanical watch that used to keep good time starts gaining minutes a day, suspect magnetism before anything expensive. Phones, laptop lids, tablet covers, speakers and magnetic bag clasps all carry strong little magnets. Once the hairspring is magnetised, its coils cling to each other, which in effect shortens the spring, so the balance swings faster and the watch gains. A watchmaker can demagnetise it in a few minutes, usually cheaply. Some watches are built to resist magnetism, and say so on the dial or in the specifications.
Quartz: a crystal that vibrates
A quartz watch passes a tiny current through a sliver of quartz cut into a tuning fork. Quartz flexes slightly when a voltage is applied (the piezoelectric effect), and a fork this size rings at 32,768 times a second. That number is 215, so a chip can halve it fifteen times to get exactly one pulse a second, and each pulse steps a tiny motor that moves the hands.
Because the beat is so fast and so steady, quartz is far more accurate than any spring: many everyday quartz watches are rated to about ±15 seconds a month. Its main enemy is temperature. Some more expensive movements measure their own temperature and correct for it, and are rated to within a few seconds a year.
A quartz battery usually lasts a few years. Change it when the watch starts to falter, or when it does the “battery low” trick some watches have of jumping the seconds hand in two-second steps. Don’t leave a flat battery in a watch: an old cell can leak and damage the movement. Our button cell guide sorts out which battery code is which.
Solar quartz
A solar watch is a quartz watch with a solar cell under the dial and a rechargeable cell instead of a disposable battery. Citizen’s Eco-Drive, Casio’s Tough Solar and Seiko’s solar range all work this way. Ordinary daylight keeps them charged, and a full charge usually runs the watch for months in the dark. The rechargeable cell wears out eventually, but it typically lasts many years. Just don’t store one in a drawer for years on end.
Radio-controlled, GPS and Bluetooth: watches that set themselves
A radio-controlled watch listens overnight for a long-wave time signal and sets itself from it. The transmitters are in Japan (JJY), China (BPC), Germany (DCF77), the UK (MSF) and the United States (WWVB). None of them reaches Australia reliably, and Australia’s own shortwave time signal, Radio VNG, went off air in 2002, and watches were never built to read it anyway. Bought here, a radio-controlled watch is simply a good quartz watch; it’ll try to sync and quietly fail.
What does work in Australia:
- GPS watches set themselves from satellites, usually when you press a button or when they see open sky. They also pick up the time zone when you travel.
- Bluetooth watches, including many Casio G-Shocks, set themselves from an app on your phone a few times a day.
- Smartwatches get the time from the phone and the mobile network, so they’re always right.
Water resistance: what the number on the back means
The metres on a watch are a pressure test in a laboratory, done once on a new watch, with the watch held still. They are not a depth you can take it to. Swimming, diving in and hot water all put more strain on the seals than a still test does. The international standard for everyday watches is ISO 22810; dive watches have their own, stricter standard, ISO 6425, which starts at 100 metres and adds tests for things like a bezel and legibility in the dark.
| Marked | Fine for | Not for |
|---|---|---|
| Water resistant, or 30 m (3 bar) | Rain, splashes, washing your hands | Showers, swimming |
| 50 m (5 bar) | A brief swim in calm water, at a pinch | Diving in, snorkelling |
| 100 m (10 bar) | Swimming and snorkelling | Scuba diving |
| 200 m, or marked Diver’s | Swimming and recreational scuba | Saturation diving, unless it says so |
Three habits keep water out:
- Screw the crown down if it’s a screw-down crown, and never pull it out or press the buttons underwater unless the watch says you can.
- Keep it out of hot showers, spas and saunas. Heat makes the seals expand and soften, and steam gets in where water doesn’t.
- Have the seals checked when the battery is changed, or every year or two if you swim with it. Gaskets dry out and harden with age, whatever the rating.
Servicing
A mechanical watch’s oils thicken over the years, and the parts start to wear. Makers suggest a service every several years, with a range of anywhere from about five to ten depending on the brand. A quartz watch mostly needs batteries and seals, though its little motor and gears can need cleaning eventually too. Either way, a service that includes a pressure test is the only way to know the water resistance still holds.
Common questions
Can I swim with a watch rated water resistant to 30 metres?
Do radio-controlled watches work in Australia?
Why is my automatic watch suddenly gaining minutes a day?
How accurate is a quartz watch?
Sources
All checked 11/11/2026. We don’t sell watches, and none of these links earns us anything.
- COSC, Chronometer certified (the ISO 3159 test and the −4/+6 seconds a day limit). cosc.swiss
- Wikipedia, Radio VNG (Australia’s time signal, closed in 2002). en.wikipedia.org
- ISO 22810:2010, Horology: Water-resistant watches, and ISO 6425:2018, Horology: Divers’ watches. iso.org