alt Hacker NewsI recently bought my first not-super-cheap watch, and found out that all around the world there radio stations which broadcast the atomic clock time that a lot of clocks/watches listen to.
After setting the time zone (I guess this also changes the frequency that it listens on) it starts to sync itself using that signal. It is also solar-charging - so this basically means that I never have to touch it. Although it's an analog watch, because of this sync, it correctly handles DST, the date window (including leap year) - basically I never have to touch it again until it breaks . All without bluetooth or internet connection - pretty cool I think.
Casio Oceanus t200 for anyone that cares.
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That “all around the world” leaves significant gaps: https://hagensieker.com/2019/11/17/multiband-6-what-is-it/
I had a weather station with an external antenna that could never sync, even during the night, even placed outside in the "best" side of the house on my neck of the EU.
A solar powered, low battery wristwatch that's never outside in the middle of the night will fare much worse.
It's interesting old school tech that works fine in the places where it does work.
For elsewhere, I guess synching through a phone is more practical. So far it works fine. I just hope it doesn't get deprecated (I do, unfortunately, have a feeling the Casio app will break before the radios stop transmitting).
I'm pretty sure it's a lot more reasonable to use a fixed set of frequences and use the timezone for offset
In the US, those are radio stations WWVB for clocks and watches, and WWV/WWVH for shortwave.
One thing I think is interesting is that not only are the digital formats these carry synced to an atomic clock, but the radio carrier wave is too. So if you need a very precise 10 MHz signal in the lab, you can hook up a shortwave antenna and a filter, and receive the precisely-on-frequency signal broadcast from WWV.