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Re: What time is it, really?



On Fri 10 Aug 2018 at 11:32:35 (-0400), Michael Stone wrote:
> On Fri, Aug 10, 2018 at 10:18:19AM -0500, David Wright wrote:
> >Currently we have a consumer radio clock which is a source of mystery
> >to me twice a year: the DST change occurs in the early evening on
> >Saturday instead of Sunday morning.
> 
> The clock isn't properly decoding the DST bits. See
> https://en.wikipedia.org/wiki/WWVB
[…]
> Your clock is probably only looking at the first bit, and skipping
> the logic for when to actually apply the change. A lot of the
> functionality in the time code actually allows for relatively
> graceful degradation like this to facilitate simpler or more complex
> receivers.

Ah, that makes sense. So the different time of the change (which meant
I didn't remember precisely what time it happened) is because of the
varying offset (5, 6 hours) in spring and autumn, and a delay after
that hour o'clock would likely indicate varying signal strength and
lapses in reliable code detection. Now I know what's happening, I can
watch for the latter. Being a dial clock, there's no signal strength
indicator. Our LCD clock does display it approximately, but that only
understands MSF, not WWVB, so it's now free-running (remarkably well
especially since the Low Battery warning has been flashing since
before Christmas).

Cheers,
David.


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