Tom, I was under the same impression as you, regarding RC clocks. However, I just pulled/replace the battery on one of mine and then forced an update. It still is an hour off. Am I missing something, or is the clock?
----- Original Message ----- From: "Tom Van Baak" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <[email protected]> Sent: Sunday, March 11, 2007 2:34 PM Subject: Re: [time-nuts] Happy Leap Hour Day ! > To address some of the recent DST postings... > > Clocks with hard-coded USA DST rules will be off by an > hour for the three weeks from 11-Mar to 1-Apr-2007. > Given how long it's been since the DST rules changed you > can see why someone in a cheap or weak moment would > design a clock with hardcoded rules. Still, a bad design. > > WWVB radio-controlled "atomic clocks", on the other hand, > do not have hardcoded rules; instead they switch to DST > based on command from Boulder. This is why many of us > saw our RC clocks/watches do the right thing this morning. > This is a good design. > > But a big problem remains. The WWVB subcode has only > the ability to give 1 UTC day of advanced warning of a DST > change. So if your clock happened to have poor reception > yesterday it still doesn't know of the DST change and will > remain in error by an hour until it ever gets good reception, > which could be day(s) later. > > The problem is compounded by the fact that most RC clocks > only enable reception late in the evening (e.g., starting at > 11 PM), that the DST switch occurs at 2 AM local time, and > that most of the USA is 5 to 8 hours left of Greenwich. > > These three factors make the window for DST notification > much smaller than one day. And the result is that every time > a DST change occurs there are tens of thousands of RC > clocks that get it wrong (by not getting it at all). It's all a little > embarrassing since these clocks are often advertised to be > accurate to a millionth of a second, etc. > > Further embarrassing is that NTP, the great internet clock is > so academically pure, and that GPS, the great clock in the > sky, is so globally available, that neither dare taint themselves > with the geographical and political mess of timezones or DST. > > A solution would be to carve out a few more DST bits in the > WWVB subcode. So instead of giving a few hours of notice > an RC clock would see, for example, a 7- or 15-day binary > countdown to the DST event. That way, poor reception the > night before DST, or even a couple of nights before, would > not make the clocks fail at 2 AM Sunday. > > Don't hold your breath waiting for a fix; but at least you better > understand the problem now. Actually, the solution may be > that more and more people are using cell phones instead of > clocks/watches/computers to get accurate local time... > > /tvb > http://www.LeapSecond.com > > > Links: > > NIST Radio Station WWVB > http://tf.nist.gov/stations/wwvb.htm > > WWVB Time Code Format > http://tf.nist.gov/stations/wwvbtimecode.htm > > WWVB Radio Controlled Clocks > http://tf.nist.gov/stations/radioclocks.htm > > http://tf.nist.gov/general/pdf/1976.pdf > http://tf.nist.gov/general/pdf/1383.pdf > > Decoding WWVB from a Sony atomic... > http://www.leapsecond.com/pages/sony-wwvb/ > > WWVB Subcode Test Generator - wwvb2 > http://www.leapsecond.com/notes/wwvb2.htm > > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
