[Frost1x]

I’ve had a Phillips “atomic” alarm clock beside my bed for 23 years that just sets based on radio signal and auto restores if the power is lost, to which it has a backup 9v battery.

There’s a time zone setting offset slider and a DST slider. I basically touch it twice a year, maybe another if I move time zones. I’ve only had to touch it for DST (never switched time zones). Takes me conservatively 10 seconds to find and flip, so it’s taken me 460 seconds or a little under 8 minutes in the past 23 years to do time adjustments.

While these efforts are definitely fun hobby projects, there are cheap reliable solutions out there with minimal intervention that consume the NIST radio signal for time.

Just for anyone interested who wasn’t aware there’s some “old school” time broadcast solutions out there too besides NTP: https://www.nist.gov/pml/time-and-frequency-division/time-di...

[petepete]

I have 4 Seiko wall clocks that are radio wave controlled. They look beautiful and other than changing the battery need 0 intervention from me. Couldn't recommend them highly enough.

Pity they don't seem to make them any more, the newer ones use GPS and don't look quite as nice (in my opinion at least).

https://www.rigbyjewellers.co.uk/products/radio-controlled-r...

[RankingMember]

It'd be cool if there was a drop-in replacement for the standard cheapo clock module that allowed you to add this for existing clocks.

Edit: It exists! https://www.walmart.com/ip/Atomic-Radio-Controlled-Clock-Mov...

Might be doing some retrofitting soon!

[ThePowerOfFuet]

Braun makes similar ones.

[moduspol]

I tried atomic clocks but they wouldn't work unless they were on the southwest corner of the house. It even said in the manual that if it's not working, to try putting it there. Kind of defeats the purpose setting itself if I have to move it to a specific corner of my house twice a year.

Though I didn't want a digital clock--my goal was an analog-style clock that never needed any maintenance. And it ends up there are some reasonably priced ones on Amazon that just connect to WiFi once a day and adjust if necessary, including to account for DST. I have it set to run at 4am each day, so any DST adjustment happens while I'm still sleeping.

The only final step is to run hardwired power to it so I don't need to change batteries, but I haven't pulled that trigger yet. Often with projects like this, it's more fun to prove out the difficult parts and I lose interest once only the easy parts remain.

[codazoda]

I was going to mention an Atomic Clock. I use one in an RV and it sets itself even outside of cell phone range. I know it uses a radio signal of some type but I have no idea how it works. It rights itself within a few minutes of time changes, battery loss, or the like.

[ksenzee]

It's fascinating reading if you're interested in finding out the details: https://en.wikipedia.org/wiki/WWV_(radio_station)

[toomuchtodo]

We’ve come full circle.

https://news.ycombinator.com/item?id=46952384

https://github.com/tanvach/clocksync

https://github.com/kangtastic/timestation

https://github.com/hzeller/txtempus

WVB: A Tiny WWVB Station - https://news.ycombinator.com/item?id=13258631 - December 2016 (49 comments)

https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

[e28eta]

I’ve thought it’d be fun to find the chip used in those clocks, and integrate it into an offline microcontroller driven clock, but haven’t found the will to do so yet. I haven’t even looked for prior art, which I’m certain exists.

[FearNotDaniel]

Or for Western Europe there is DCF77 https://en.wikipedia.org/wiki/DCF77

[m463]

I did went GPS+ntp route.

I have a few raspberry pis on my lan that serve NTP time. (you need more than one)

Over the years I've experimented with various flavors.

Right now I have a mix:

1) a pi3 with a gps hat and a battery backup for the pi itself. It uses ntp 127.127.20.20 for gps time, and 127.127.20.28 for PPS. The SMA antenna goes to receiver at the window

2) a pi3 with USB gps on a cable going to the window

3) a pi4 same as above, but with a tiny battery backup rtc attachment

4) a pi5 with usb gps + the new RTC with an added rechargable battery backup

usually, when power goes out, a few reboot, but #1 stays up if <1hr without power. If power outlasts the pi with battery backup, the RTC battery backups take over. strangely #1 doesn't reboot when it has power, some artifact of the battery backup hat - I have to manually reset it.

I've also kind of wondered if GPS might be able to give you a time less accurately but quicker. Sometimes I look at the NMEA GPS output, and it sometimes doesn't have a position fix, but it does give out a time + week number

(this is all for no good reason, just yak shaving.)

[seba_dos1]

> I've also kind of wondered if GPS might be able to give you a time less accurately but quicker. Sometimes I look at the NMEA GPS output, and it sometimes doesn't have a position fix, but it does give out a time + week number

No. Accurate time is one of the prerequisites for acquiring a position fix, and it's the one that's the easiest and fastest to obtain from the sky. Typically a receiver should be able to get time within seconds from cold start if there's enough sky visibility, and once it does it is as accurate as it gets regardless of position fix status (unless you care about sub-nanosecond precision, but you need to be able to somehow consume that anyway and you won't with a Pi).

That said, NMEA output will usually contain the time from the module's internal clock that gets synchronized with GPS time when available rather than GPS time directly. Some modules can be configured to report when they have synced their time though, and you could pay attention to the time jumping to infer it too.

[rcxdude]

>Typically a receiver should be able to get time within seconds from cold start if there's enough sky visibility, and once it does it is as accurate as it gets regardless of position fix status.

It'll be good to far better than seconds when it first gets a signal and will get more accurate (microseconds to nanoseconds) once it has a position fix because it can then compensate for the delays in the signal propagation (you can think of a gps fix as a 4d fix because it also needs to solve for time). You will probably need to use the PPS output to resolve this, though.

[seba_dos1]

What I meant was that it will take seconds to get an accurate time from the sky (as accurate as it gets without specialistic techniques or equipment to consume it, and better than NTP already).

[colechristensen]

For a cold start, you have to wait 30 seconds for the whole ephemeris data to be broadcast unless you have another data path getting you A-GPS data. (it's literally just broadcast that slowly)

You can still get pretty accurate time (microseconds) with the GPS almanac which is broadcast over ~15 minutes and only updated every few months.

Doing really fast time acquisition isn't a hard problem but it's a hardware problem, you can't really change how an ordinary GPS receiver operates, you have to have a custom receiver.

[mark-r]

I once researched how accurate GPS time is, and the answer is it's within 40 ns. Good luck finding a way to transmit that to your CPU that doesn't add a much larger delay.

[m463]

I kind of think the ntp driver could handle this in an elegant way.

have a driver at 127.127.20.20 -> nmea time

make it normal stratum ntp, like stratum 1 or 2

doesn't give out the time unless there is a position fix (normal behavior)

and make another driver 127.127.20.99 -> nmea time without position fix

at the start, there is no time given at all

then you might get a time without a position fix

then you get a time with a position fix

then you might lose the position fix, but still give out a time.

make it a stratum 14 ntp server

[Dylan16807]

> if there's enough sky visibility

Which is a thing we shouldn't be requiring here. Picking up a single satellite without any position data is enough to drive a clock.

[seba_dos1]

You need enough sky visibility to discern signal from a single satellite from the background noise without having accurate time and recent enough almanac already.

[conorcleary]

That 'three words' grid-hex system seems a lot cheaper and doesn't rely on time-space constraints in this light

[isomorphic]

Floridian here. WWVB has never worked for me indoors (never tried outdoors). I've tried multiple vendors' clocks in multiple houses (wood frame and concrete). I assume the coverage is fine outdoors or with a sufficiently large antenna, but none of the clocks I've seen even have a mechanism to connect such an antenna. I could hack one, but then it would probably stop being cheap and reliable.

I'd love to buy an off-the-shelf WiFi+NTP clock, but everything I've seen is very expensive, intended for commercial timing applications or synchronizing clocks across a campus.

[MengerSponge]

You can spoof the wireless signal if you don't get coverage. There are surely more and better Android options, but I used Clock Wave to set a clock from Germany back in the US.

https://cw.rzapps.com/

It's really clever! It uses the speaker as the low frequency transmitter. It doesn't sound right, but it only needs the coil to radiate EM waves.

[js2]

Ditto in NC. I got this WiFi/NTP clock a couple years ago. Works great if you want an analog clock:

https://www.amazon.com/OCEST-Wall-Clock-12Inch-Auto/dp/B0DJS...

[moduspol]

I just deleted my sibling comment because I was recommending the same clock. I set it to do its daily WiFi time sync at 4am so that any DST adjustment happens before I wake up. No issues so far.

I have two of them. One project on my list is to see if I can modify the face of it to a different style without breaking it.

[RossBencina]

Australia here, no radio time as far as I know. Lately I've been wondering whether accurate time could be derived from terrestrial digital TV signals.

[maratc]

You can set your clock with an iPhone app or a computer with a pair of speakers. https://timestation.pages.dev

[whatsdoom]

This site is really cool! Thanks for sharing

> Because it works by exploiting this leakage, Time Station Emulator works best with a built-in speaker of a phone or tablet.

> In some cases, wired headphones or earbuds may also be suitable.

> Higher-frequency harmonics are considered artifacts beyond the range of human hearing, so they are routinely suppressed by audio compression algorithms and better equipment.

> Bluetooth devices and audiophile-grade equipment are therefore less likely to work.

[all2]

My solution to this is to not have clocks in my house at all.

This has nothing to do with the fact that I still haven't figured out how to set the time on my microwave. :D

[dingaling]

Clocks on microwaves seems to be a curiously American custom, driven by the fact that US outlet sockets generally don't have switches.

In Europe, and the UK particularly, every socket has a switch so the microwave is turned off after each use.

[pgh]

It might be switched off after each use in your household but it’s definitely not in others. Neither is the toaster, nor kettle.

[raverbashing]

Yeah stuff like this fits the "old school" definition https://en.wikipedia.org/wiki/Time_signal#Electrical_time_si...