[time-nuts] Happy Leap Hour Day !
jgray at zianet.com
Sun Mar 11 16:44:14 EDT 2007
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" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
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...
> NIST Radio Station WWVB
> WWVB Time Code Format
> WWVB Radio Controlled Clocks
> Decoding WWVB from a Sony atomic...
> WWVB Subcode Test Generator - wwvb2
> time-nuts mailing list
> time-nuts at febo.com
More information about the time-nuts