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Clocks that rely on AC power frequency have always been inaccurate. That fact annoyed me since I was a kid, and I always opted for quartz clocks for that reason. According to these test results, AC power in the US can drift from 30-70 seconds per typical day. This is in keeping with my own experience.

Those companies that were "successful" at manufacturing AC-driven clocks were successful because there was no better option at the time, or people didn't care enough about time precision. AC has never been a great way to keep time.

Nah, that one's not digital enough. It'll look something more like this

This amateur has done what you're looking for: http://leapsecond.com/

The whole problem strikes me as one of human preferences, not technical requirements. There's absolutely no reason not to use our atomic clocks and just count number of seconds since some starting point. The desire to have the sun directly overhead at "noon" is a human one, divorced from any technical requirement. All of science, computing, networking, telecommunications, would be much happier if we didn't continually redefine time like this.

So let watch manufacturers and clock-app manufacturers deal with this, when reporting time for human consumption. It shouldn't be a problem for NIST and government bodies. NIST should instead be reporting Earth's orbital parameters as time delta from noon, as they change over time, not conflating time itself with Earth's orbital parameters.

This is the way GPS, Loran-C and TAI handle time, and it's the right thing to do.

Is there some standard way to manage timing? Does the weekend hacker need to deal with signal/buffer latency from the DAC/ADC or somehow manage timecode synchronization?

The DAC and ADC are clocked by the master 10 MHz oscillator, and there's a gate-array that you can program all sorts of hardware timing into. But if you are actually dealing with radar I would expect that you've already joined this mailing list.

Between this and the WWVB anniversary it's been a good run the last few days for time nuts.

"A man with one clock knows what time it is. A man with two clocks is never sure. But I would add further: A man with three clocks is more sure than a man with two clocks."
Quoted from one of the quintisential time nuts at
http://www.leapsecond.com/

For the discerning measurement enthusiast, the first ever atomic wristwatch!

http://leapsecond.com/pages/atomic-bill/

That said, I bought a new watch recently. I had four criteria:
- Maintenance free - electronic but no need for battery replacement (mechanical watches need an oil change every few years)
- Radio controlled, receiving all three standards (OK that kind of includes the one above)
- Titanium case
- at least moderately waterproof.
That whittled it down to a manageable set and when I saw a Citizen Nighthawk on sale I hit it.

I've been using one of these for years.

This guy has had a real atomic wristwatch for at least a decade. http://leapsecond.com/pages/atomic-bill/

I would expect US NIST Time & Frequency division or US Naval Observatory Time department would be more than willing and able to host the zoneinfo database. Otherwise the time-nuts would likely step in and offer their support. A number of them being long time Unix folk, they wouldn't be total strangers to IANA or various national time authorities.

Apparently, the US National Institutes of Health (NIH)...for some strange reason...has been hosting the project. (Off the top of my head, I know that NIH also developed Image and ImageJ, presumably for their own needs.)

<republican>Sounds like more government waste to me. Why is NIH in this business exactly</republican>

I would expect US NIST Time & Frequency division or US Naval Observatory Time department would be more than willing and able to host the zoneinfo database. Otherwise the time-nuts would likely step in and offer their support. A number of them being long time Unix folk, they wouldn't be total strangers to IANA or various national time authorities.

You're that guy from Leap Second, aren't you? ;-)

If you just wanted an atomic wristwatch here is the first real atomic wristwatch. Not those fakes which use radio reception

http://www.leapsecond.com/pages/atomic-bill/

A decent analog watch has superbly-crafted components and therefore deserves the admiration. A decent digital watch needs something marginally better than a 555 timer, but only marginally.

That's not to say I wouldn't gave respect for a digital watch with the accuracy and drift of a scientific high-precision timer. I'd consider it adequately impressive for a digital watch to have a drift of a few nanoseconds a day.

(I'm judging analog differently than digital in the resolution, but really about the same in terms of the effort required to produce a system of a given standard because that's the only measure of craftsmanship you can ever really have.)

I guess you've never seen the tv out feature that normally comes with nokia phones.

As opposed to bringing a laptop, you suggest bringing a TV set and a generator to use with your phone? Impressive.
May I interest you in this handy and accurate wristwatch as well? :)

when events happened

That's what I said, past events and the current time should be stored in GMT (or GPS or whatever the hell standard you want to use).

But future events... if I store an appointment in GMT, and the government declares that the conversion factor will be different by 30 minutes, then I've got to go back through every stored appointment and revise them, before I allow anyone to add any new ones to the system. Especially on a Unix system, where timezone data is usually centrally administered and was automatically apt-got weeks ago before anyone thought about running the script that changes all the appointment times by 30 minutes.

Good question about the 22 ns. Unlike the airplane experiments, because the van traveled slowly (60 mph max) and only for a few hours getting to and from the mountain, the relativistic effect due to velocity alone would be about 0.05 ns, or 50 picoseconds. Too small to worry about.

The dominate effect for this experiment, since the van and clocks just sat still a mile-high for the weekend, is the gravitational relativistic effect. The GR time dilation rate is approximately gh/cc, which for an elevation gain of 1340 meters and a stay of 42 hours, comes to about 22 nanoseconds.

More info on the trip is at http://www.leapsecond.com/great2005/

Oh, you mean the way Unix has done it for close to 1,200,000,000 seconds? Of course, the timezone handling, including leap seconds, is much more sophisticated now than it was then, but the leap second is a solved problem. Eliminating it won't even make any code simpler, since the libraries still need to handle the leap seconds we've already encountered.

Any device that needs to do accurate timing AND be exactly consistent with the official time needs to use something pretty much exactly the way Unix does it, and there's absolutely no reason why it can't. A majority of devices that keep time drift more than a second a day anyway, so a leap second gets subsumed in periodic corrections of that time, whether done automatically (NTP or WWV or GPS or whatever) or manually. Anything using "wall clock" for timing is already confused twice a year by the DST shift. In addition, using a good time library completely eliminates any other silly Y2K-like scenarios in the future (e.g. 2100 is going to be a similar problem).

Anyway, the time base you're looking for is called TAI, and is currently 33 leap seconds ahead of UTC.

The Atomic wrist-watch already exists, it's just a bit bulky.

That reminds me of the first atomic wrist watch.

Dun dun dun.

Actually, atomic wristwatches already exist.

http://www.leapsecond.com/pages/atomic-bill/

like this???

http://www.leapsecond.com/pages/atomic-bill/

I'm just waiting for the wristwatch version.

Can't wait to have a wristwatch with this. My atomic wristwatch is a bit too bulky.

you need an atomic wristwatch (and not one of those radiocontroled ones)

http://www.leapsecond.com/pages/atomic-bill/

It is worth noting that those "leap seconds" amuse only some people. People who work on systems that can't afford a 1 second discontinuity (such as the GPS system) use a continuous counting of the SI second.

http://www.leapsecond.com/java/gpsclock.htm

If you want the ULTIMATE in clunky, difficult to wear watches, you need one of these:

http://www.leapsecond.com/pages/atomic-bill/

One hell of a lot more accurate than that nixie tube toy! :)

There are multiple standards already ( http://www.leapsecond.com/java/gpsclock.htm )

UTC, GPS (+13sec from UTC), Loran (+22sec from UTC), TAI (+32sec from UTC).

The only difference this time is that they want to break UTC which us everyday folk use.

To correct this, change the number of cycles of the Cesium or Rubidium atomic frequency in the definition of time, or make the Earth turn slower.

I'm positing that it's much easier to change the number in the definition of time than it is to change the period of the Earth's rotation.

To avoid a gratuitous /.ing of what would appear to be a private site here's the start of www.leapsecond.com

======

Ten years ago I wanted to build a LED digital analog clock that would be accurate to better than one second per year -- so I would have the fun of adjusting it when a leap second occurred. This simple goal resulted in a most interesting journey into electronics, horology, astronomy, test equipment, quartz oscillators, rubidium and cesium atomic clocks, hydrogen masers, frequency counters and phase comparators, GPS, Loran C, GOES, and WWV / WWVB radio receivers. By now I've exceeded that goal by a factor of a million: the best clocks in my collection (active hydrogen masers) are accurate to better than one microsecond per year. Excluding national government laboratories, my home time lab now has the most accurate clock in the world. That makes me one of the time-nuts. Perhaps you've heard: A man with one clock knows what time it is. A man with two clocks is never sure. But I would add further: A man with three clocks is more sure than a man with two clocks. And so the clock collection started...

======

Take it easy folks.

Not the same mechanism as in the article, but will this satisfy your needs?

And in 2003, a leap-second bug made GPS receivers from Motorola Inc. briefly show customers the time as half past 62 o'clock.

If I remember correctly, this was caused by the fact that a counter in the code that incremented each week there wasn't a leap second wrapped around. They knew about it in advance, and were able to warn people to reset their receivers.

Removing leap seconds altogether is silly, until we have the technology to rearrange the solar system to match our clocks. And when we can do that, we may as well go to decimal time...

Mark

PS What do you know, I did recall correctly :) You can also view Motorola's original PDF advisory which interestingly doesn't think the time will be wrong, just the date.

Maybe we should all consider wearing one of these atomic wristwatches to keep track of all these changes.

http://leapsecond.com/ -- This guy should complain. They're taking all the fun out of his clock collection!

It is solar powered too

I don't care. I have an atomic watch that will automatically adjust. It is solar powered too, so I never have to worry about the bateries running down either. I love my watch.

You must be really strong. I didnt know the HP 5071A was solar powered though. :-)

I just wanted to be the first to mention this site, someone wanted to view the previous leap second, and that became an obsession.

Okay, here's a clickable link:
http://leapsecond.com/

An obsession in another are of time is this Y10K Compliant clock:

http://longnow.org/

Or a couple of nylon bands. A paper-thin display on that puppy ain't gonna make it "wearable" by the skinny nerd brother in law who "invented" it.

...the worlds first atomic wristwatch.

That guy has clocks accurate to better than 1 part in 10^13, which means that the clock will only be wrong in its count of 9,192,631,770 vibrations/second once every thousand seconds.

And the ultimate Rolex-beater completes the picture of the modern major motion picture director.

You might want to be more specific about your requirements. Remember the atomic wristwatch?

Does this mean there will be an upgrade to the current atomic clock wristwatch?

My favorite quote is "Batteries are included (they last about 45 minutes but are rechargeable)."

Call me back when there's a portable version available.

I guess this guy will need an upgrade.

Slashdot hurts my brain.

I couldn't agree more.

Thanks for drawing my attention to the site... those nixie-tube clocks are a real treat.

Also, take a gander at this.
I am humbled by the utter geekery of such a sight.

Can I run two GeForce6800 Ultras in a single VESA Local Bus slot on my 486 DX266?

I'm sure some geek somewhere has made an adapter for it...They get bored just making costumes, atomic watches and chess sets.

Can I run two GeForce6800 Ultras in a single VESA Local Bus slot on my 486 DX266?

I'm sure some geek somewhere has made an adapter for it...They get bored just making costumes, atomic watches and chess sets.