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Discussion Starter · #1 ·
A little confused at first as to how my GW-M5600 and GW-M5610 both synced this morning at 01:05 and 01:04 respectively (one hour before DST finished), and yet both knew to revert to GMT.

I checked the manuals and they actually sync for the first time at 02:00 whilst running in DST, and then knock off that additional hour.
Next March they'll sync at 01:00 GMT (UTC+0) and then add an hour on.

Obviously this is so that when you check the RCVD time, it'll be correct for the time mode you're currently in.

I knew the change couldn't be programed into the calendar because my non-atomics have to have the DST mode changed manually and not all countries observe changes on the same day, or at least haven't always.

Just thought I'd post that in case anyone else was puzzled as to how their radio-controlled clocks and watches could be so smart......simple really!

NB. Bit of a moot point though, as we're scrapping the whole clock change business at some point next year.
 

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Oh I see. Well, in addition to summer time bits, there is a bit in time signal which is called "Summer time announcement" (Ref: DCF77 - Wikipedia). Probably the watches use it to know in advance when it is time to turn on/off the DST.
 

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Did they not sync at 02:04 and 02:05 and adjust the sync time to match the new correct time?

Also 2 of mine updated the dst but don't show rcvd on the display, how does that work?

Edit, tiha may have answered my own question
 

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Discussion Starter · #6 ·
Did they not sync at 02:04 and 02:05 and adjust the sync time to match the new correct time?
Yep, that's exactly what they did but I either wasn't aware or had forgotten that they shift the sync times according to the GMT/DST mode currently in operation.
 

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I just got this notification (moments ago) on my phone. We are not due to switch from DST to standard time until Nov 1st. What's up with that???

15516911
 

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Discussion Starter · #8 ·
I just got this notification (moments ago) on my phone. We are not due to switch from DST to standard time until Nov 1st. What's up with that???

View attachment 15516911
Is Nov 1st normal for you?
It was agreed some years ago that all countries in Europe (that observe DST) would alter their clocks at the same time - last Sunday in March / October.

Perhaps your local state has its own zone, so to speak, and maybe you've recently crossed state borders.

Interesting!
 

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Is Nov 1st normal for you?
It was agreed some years ago that all countries in Europe (that observe DST) would alter their clocks at the same time - last Sunday in March / October.

Perhaps your local state has its own zone, so to speak, and maybe you've recently crossed state borders.

Interesting!
No... I'm in the U.S. Nov 1st is the nationwide date (with the exception of Arizona, I think). I'm not in Arizona.

But, I think maybe I figured it out. It may be related to my World Time set to London. They changed today, apparently. So, maybe it's because of my World Time zone.
 

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The UK station may have a different policy on updating DST informstion, but the US-American Ft. Collins DST reference signal will be set / goes out way before midnight.

Our atomic wall clocks sync (many times per day) and they do so at around 20.00hour PRE-midnight of DST change AND already get the UPDATED DST information.
 

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It was agreed that all EU member states would stick to the same date but that doesn’t apply to non EU countries.
 

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The UK station may have a different policy on updating DST informstion, but the US-American Ft. Collins DST reference signal will be set / goes out way before midnight.

Our atomic wall clocks sync (many times per day) and they do so at around 20.00hour PRE-midnight of DST change AND already get the UPDATED DST information.
My understanding is that the WWVB DST bit is turned off/on at 0:00 UTC. For Pacific time in the US, this will be 5 PM the day before DST is to be turned off and 4 PM the day before DST is to be turned on. For Eastern time, this will be 8 PM and 7 PM, respectively.
 
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Discussion Starter · #14 ·
That is interesting.
I think my wall clock always syncs at 2am and only does so once if successful.
Of course at 2am the time will always be correct with regard to DST status and syncing once helps to save battery power - it does the 10 hour (to the 12 o'clock position) sweeping hands thing before settling on the correct time.
Not normally a problem at that time in the morning, but several times before and after midnight would render the clock useless as a timepiece during those periods.....if it were analogue.
 

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Discussion Starter · #15 ·
My understanding is that the WWVB DST bit is turned off/on at 0:00 UTC. For Pacific time in the US, this will be 5 PM the day before DST is to be turned off and 4 PM the day before DST is to be turned on. For Eastern time, this will be 8 PM and 7 PM, respectively.
Yes, but your clock would only 'look' for the signal at the appropriate time for your location.
My temperature station/clock only sees the transmitter in Germany and by default sets that time, so I have to set it up for the UK time zone for it to be correct.
I doubt any clocks are programed to receive a signal but then ignore it until a specified time later ie. "I've got to change the time and turn off the DST indicator but not for another two hours".
 

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Yes, but your clock would only 'look' for the signal at the appropriate time for your location.
My temperature station/clock only sees the transmitter in Germany and by default sets that time, so I have to set it up for the UK time zone for it to be correct.
I doubt any clocks are programed to receive a signal but then ignore it until a specified time later ie. "I've got to change the time and turn off the DST indicator but not for another two hours".
In the US, my MB6 watches first look for the WWVB signal at midnight, and they will turn DST on or off at this time, even though technically the change is not supposed to happen until 2 AM.
 

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Discussion Starter · #17 ·
In the US, my MB6 watches first look for the WWVB signal at midnight, and they will turn DST on or off at this time, even though technically the change is not supposed to happen until 2 AM.
Yes, that what the manual says for module 3159 - midnight for both normal and DST times for the US.
I wonder why Casio have specified that when as you say, technically the time will be wrong for a couple of hours or at least the DST indicator will be on or off when it shouldn't be.
 

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Yes, that what the manual says for module 3159 - midnight for both normal and DST times for the US.
I wonder why Casio have specified that when as you say, technically the time will be wrong for a couple of hours or at least the DST indicator will be on or off when it shouldn't be.
At least it gives two more opportunities to sync every night, and the "problem" only happens twice a year.
 

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Like others said, my experience is the DST on/off info is embedded in the radio signal hours before it officially starts. I used to manually sync around 11pm the night before the switch, and it was already there.
 
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