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Discussion Starter #1
Since daylight savings time begins and ends at 2:00 AM and the atomic set starts at midnight, is it different on those two nights? Does the watch set multiple times on those two nights so the time is correct the next day when you get up or what happens since normally if there is a sucessful set another set does not happen till the next night.
 

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Discussion Starter #3
I'm going to rephrase the question because it seems it is not understood. I understand that the signal sends if it is DST or standard time. That is not the question. The question is on the night that the change takes place it is still the old time at midnight and 1:00. At 2:00 AM the time changes but if the watch already had a successful set it will be wrong for a day.

Example:
Midnight the watch receives DST set and is successful so it will not set again, but at 2:00AM the signal goes out that it is now 1:00 standard time because the time changed but the watch it seems will not get that correct time because there was already a successful set. That means you need to do a manual set when you wake up.
 

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Good question! Compounded by the fact that the date on which DST starts and ends in the U.S. changed a few years ago, and some of the older watches may not account for that? I thought the DST change was done internally when the watch hits a certain date? For sure the correct time would be set on the atomics the day after DST starts I guess on the next nightly synch?
 

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I had an atomic G several years ago and the last receive was always 04:00 so it wasn't an issue. I'd check what yours does now- if the last "get" is before 02:00, do a manual reset in the morning and assume it hasn't updated until proven otherwise if it might affect your punctuality.
 

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Good question! Compounded by the fact that the date on which DST starts and ends in the U.S. changed a few years ago, and some of the older watches may not account for that? I thought the DST change was done internally when the watch hits a certain date? For sure the correct time would be set on the atomics the day after DST starts I guess on the next nightly synch?
The date DST commences and ends should have no impact. For "atomic" G-Shocks, the time change is based on reception of the radio signal -- not some internal setting. When the information in the radio signal changes, the watch data will change.

Intriguing question, though, about the mechanics on the day of the time change. Since the atomics I keep in the window are generally reset to the proper time by the time I wake up in the morning, the system works somehow!
 

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It's actually quite clever how it works. (I'm talking about the US time signal WWVB here.)

There are a number of different states that the time signal can be in:

  1. DST is not in effect
  2. DST begins today
  3. DST is in effect
  4. DST ends today
So if the watch syncs before the DST changeover, it will receive the flag saying that DST begins today, so it will know that it needs to change over later on at the correct time for the changeover. The signal is warning the watch "We're not in DST right now, but we will be later. So when your clock reaches 02:00, turn on DST mode."

It works similarly for DST ending.

Check out the Announcement Bits section of the WWVB wikipedia article.
 
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