20 seconds a month is about normal for a quartz watch.
Quartz is (generally) accurate to about 0.5 seconds a day. (It varies, mostly by temperature.) Compare to a good quality mechanical watch, which is accurate to about 3-5 seconds a day. Cheaper mechanical watches, considerably less.
Casio "wave ceptor" watches receive the time signal every night, and so don't drift. Some other more expensive watches sync with the GPS signal, or with bluetooth to your phone.
If you demand accuracy without a regular sync, so called "high accuracy quartz" watches do exist, which can be accurate to about 15-30 seconds per year. The Bulova "Precisionist" line of watches are good examples of these.
> 20 seconds a month is about normal for a quartz watch. [...] so called "high accuracy quartz" watches do exist, which can be accurate to about 15-30 seconds per year.
Heh, you can get much better quartz watches than that if you're willing to pay for it. I have a Grand Seiko 9F super high accuracy quartz watch (SBGP017 is the model number if you're curious) that has gained just a little over a second in the year that I've had it. Citizen also makes high end quartz watches with similar accuracy (look up the Chronomaster).
Diminishing returns, probably, especially if you live in a location where you're going to be setting your watch twice a year anyway for daylight saving.
My SBGP017 has a jump-hour movement that I can use for DST (or while traveling) to set the hour hand without hacking the seconds hand. That's how I know its accuracy over an entire year, even though I've adjusted it for DST twice since I got it and done some international traveling as well. I'll literally only ever need to set the time once every battery change.
Of course it's diminishing returns regardless, but the accuracy achievable is nevertheless impressive.
That's actually a normal amount for any watch. A well-maintained Rolex is +- 5 seconds a day. AFAIK, only the 'atomic' watches or ones sync'd against your cellphone do better.
Also, 20 seconds means <2 min drift between the adjustments you make for daylight savings time.
The F91W is like $20 though. You're expecting too much from something so cheap. If you pay a bit more than that you'll get a better product. The profit margins on a $20 watch are too low to individually calibrate the rate accuracy of each one, which is the bare minimum that you need to compensate for the manufacturing differences on each individual quartz crystal. And then for accuracy beyond that you would need thermo-compensated quartz, though you only see that on models costing in the 4 figures so if you only care about price performance, you'd sooner get a radio/GPS-controlled model.
Quartz is (generally) accurate to about 0.5 seconds a day. (It varies, mostly by temperature.) Compare to a good quality mechanical watch, which is accurate to about 3-5 seconds a day. Cheaper mechanical watches, considerably less.
Casio "wave ceptor" watches receive the time signal every night, and so don't drift. Some other more expensive watches sync with the GPS signal, or with bluetooth to your phone.
If you demand accuracy without a regular sync, so called "high accuracy quartz" watches do exist, which can be accurate to about 15-30 seconds per year. The Bulova "Precisionist" line of watches are good examples of these.