The cause is that the watch module follows the time signal's dst information (starting, on, ending, off) WWV (radio station) - Wikipedia, the free encyclopedia
Some watch modules use the time signal dst info and others don't
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Interesting Find: Auto DST in GW-3000B
Found something interesting in my new GW-3000B (Module 5121): at least in the USA, it sets Daylight Savings Time (DST) to "on" when it synchs within the four continental USA time zones.
Here's the situation: I'm in Arizona, where it's MST year-round (except for the Navajos).
1. Set my home city to Denver (DEN).
2. Set DST to off (the indicator says STD, meaning standard time).
3. Returned to normal mode, and everything is kosher.
4. Let the watch synch overnight.
5. Next morning, watch is an hour ahead, and when I display my home time zone, it still shows it as Denver, but with DST "on".
6. Checked the synch indicator, and it says "Y" (Yes, I synched).
So... I figured I made a mistake with the home time zone, so I tried it again. Very carefully following the manual.
Next morning, guess what? Denver is magically set to DST "on" again. Tried this two nights running, with the same results.
Conclusion?
The GW-3000B has an undocumented auto-DST feature. Only thing that I could find supporting this in the manual was this cryptic entry: "As of November 2009, China does not use Daylight Savings Time (DST). If China does go to the Daylight Saving Time system in the future, some functions of this watch may no longer operate correctly." In other words, there is an automatic DST setting for certain time zones, and China is not currently one of them (implying that other zones, namely North America and maybe Europe, are).
I'm posting this for the benefit of others in non-DST locations (AZ, IN), who might otherwise be scratching their heads, thinking that they did something wrong by setting their watch to the correct time zone, overriding DST, and then finding the watch an hour off after a successful synch.
Personally, I'd rather Casio left well enough alone, and allowed an override of DST for every time zone, but there you have it. My fix for the thing, of course, is to simply set my home city to LAX for Summer, and DEN for Winter... oh how I wish they had an AZ zone on their watches.
Here's the situation: I'm in Arizona, where it's MST year-round (except for the Navajos).
1. Set my home city to Denver (DEN).
2. Set DST to off (the indicator says STD, meaning standard time).
3. Returned to normal mode, and everything is kosher.
4. Let the watch synch overnight.
5. Next morning, watch is an hour ahead, and when I display my home time zone, it still shows it as Denver, but with DST "on".
6. Checked the synch indicator, and it says "Y" (Yes, I synched).
So... I figured I made a mistake with the home time zone, so I tried it again. Very carefully following the manual.
Next morning, guess what? Denver is magically set to DST "on" again. Tried this two nights running, with the same results.
Conclusion?
The GW-3000B has an undocumented auto-DST feature. Only thing that I could find supporting this in the manual was this cryptic entry: "As of November 2009, China does not use Daylight Savings Time (DST). If China does go to the Daylight Saving Time system in the future, some functions of this watch may no longer operate correctly." In other words, there is an automatic DST setting for certain time zones, and China is not currently one of them (implying that other zones, namely North America and maybe Europe, are).
I'm posting this for the benefit of others in non-DST locations (AZ, IN), who might otherwise be scratching their heads, thinking that they did something wrong by setting their watch to the correct time zone, overriding DST, and then finding the watch an hour off after a successful synch.
Personally, I'd rather Casio left well enough alone, and allowed an override of DST for every time zone, but there you have it. My fix for the thing, of course, is to simply set my home city to LAX for Summer, and DEN for Winter... oh how I wish they had an AZ zone on their watches.
