Atomic Timekeeping... How does it work?

Thread: Atomic Timekeeping... How does it work?

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  1. #1
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    Question Atomic Timekeeping... How does it work?

    Hi all,

    Dumb question maybe, but I was wondering how this works:

    If I have a watch, let's say the GW-400J, and I have the location set to Los Angeles... then I travel to New York... will it then set the time to NYC time during the automatic calibration at night, or do I have to actually change the location for the watch to be able to display the correct time?

    So basically, how does the watch know which time to display from the signal it picks up? How does it know in which part of the US we are?

    Thanks!

  2. #2
    Moderator G-Shock Forum
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    Re: Atomic Timekeeping... How does it work?

    The watch gets the single time signal from US (fort collins).
    The it calculates the time based on the time zone set.
    So the watch doesnt know where you are, its just looking for the time zone set.

  3. #3
    Member WhtShadow's Avatar
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    Re: Atomic Timekeeping... How does it work?

    As D2mac said, the watch only knows where it is (time zone wise) based on you setting the city. This is different than for your cell phone. Your cell phone gets the time from a local tower, so as you travel, it will continuously adjust based on the local tower.

    Have we sufficiently answered your question?
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  4. #4
    Member Vintage's Avatar
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    Re: Atomic Timekeeping... How does it work?

    Quote Originally Posted by watchgirl View Post
    Hi all,

    Dumb question maybe, but I was wondering how this works:

    If I have a watch, let's say the GW-400J, and I have the location set to Los Angeles... then I travel to New York... will it then set the time to NYC time during the automatic calibration at night, or do I have to actually change the location for the watch to be able to display the correct time?

    So basically, how does the watch know which time to display from the signal it picks up? How does it know in which part of the US we are?

    Thanks!
    Hi Watchgirl,

    You have to manually change your home time every time you change time zone in the US only if you want; only if you want. If you want your watch to show NYC time as home time, for example, because you're already there or you're flying there from LA, then you can change it.

    But if you want, you can also keep track of your time via World Time mode. In this case you keep your home time as LA, but you display NYC time in World Time mode.

    Following one method or the other is really a matter of personal preference, or of how many days you'd be in NYC, in this case.

    The watch will keep on syncing with Fort Collins in both cases.

    Edit: Ah, and I forgot. There's the Arizona case during DST elsewhere in the US. In almost all of Arizona there's no DST; never. I know it well because Sonora (where I live) and Arizona share the same time zone; no DST in both. If you go to Phoenix during DST in LA, you'd have to use the Denver time zone, where DST also applies.

    In this case you have to turn off DST in Adjust mode, so the Denver time zone can reflect Arizona non-DST time. When you do this you lose your home time syncing, be it by setting Denver as your home time or by displaying Denver in World Time mode and turning off DST there. If you don't turn off DST in Adjust Mode or World Time Mode, your watch will show Denver DST time, that is, the wrong time for Arizona (1 hour ahead).

    But once you do this, the watch will sync correctly with the US atomic clock.
    Last edited by Vintage; June 21st, 2008 at 16:36.

  5. #5
    Member Joakim Agren's Avatar
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    Re: Atomic Timekeeping... How does it work?

    It is called Time Calibration signal not Time Sync, in that signal beeing broadcasted from the radio tower there is only a pulse signal that helps time devices sync up their digits with the atomic time. It does not however contain any precise time info only sync info. For the proper time your watch rely on the home site setting.

    One might see those time pulses beeing broadcasted as replacement for human fingers. Just like you use your finger to push the button on the watch at the precise right moment when you sync it against another watch. The atomic time signal is that "finger" it helps the watch sync right within a second. But unlike you the signal has no brain and as such dont know any digits just their sync.

  6. #6
    Member dudegalea's Avatar
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    Re: Atomic Timekeeping... How does it work?

    Quote Originally Posted by Joakim Agren View Post
    It is called Time Calibration signal not Time Sync, in that signal beeing broadcasted from the radio tower there is only a pulse signal that helps time devices sync up their digits with the atomic time. It does not however contain any precise time info only sync info. For the proper time your watch rely on the home site setting.

    One might see those time pulses beeing broadcasted as replacement for human fingers. Just like you use your finger to push the button on the watch at the precise right moment when you sync it against another watch. The atomic time signal is that "finger" it helps the watch sync right within a second. But unlike you the signal has no brain and as such dont know any digits just their sync.
    Maybe I'm misunderstanding what you're saying, but the time signal does contain the full date and (UTC) time information. If you reset the watch completely to its factory state, and then do a sync, it gets the full date and time from the signal.




    It remains true, however, that the watch relies upon the home city setting in order to work out what the time is at your location, because it can't know that from the signal.

  7. #7
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    Re: Atomic Timekeeping... How does it work?

    The simple answer, from all this is:
    *No, the watch will not sync to the correct hour if you fly across the country, unless you change the timezone manually.
    *Yes, the watch will sync to the correct minutes and seconds (and date).


  8. #8
    Member Jim R's Avatar
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    Off Topic post Re: Atomic Timekeeping... How does it work?


  9. #9
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    Re: Atomic Timekeeping... How does it work?

    Quote Originally Posted by WhtShadow View Post
    As D2mac said, the watch only knows where it is (time zone wise) based on you setting the city. This is different than for your cell phone. Your cell phone gets the time from a local tower, so as you travel, it will continuously adjust based on the local tower.

    Have we sufficiently answered your question?

    Yes, thank you very much to everybody that responded!

    :thanks

  10. #10
    Member natornate's Avatar
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    Re: Atomic Timekeeping... How does it work?

    In multi band versions of the watches the timezone also points to what atomic clock the signal will be coming from. Helpful to know when you want to "trick" the watch into attempting to get time from Tokyo while in Australia (for example). I know several here have claimed to have success with that. If they had simply left their time set to local it would by default not even look for a signal as there is not one that Casio deems close enough to Australia to attempt to sync with.
    -Nate
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