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DST and the four-switch solution - The online computery journal thingy of a turtle — LiveJournal

Mar. 12th, 2007

07:54 pm - DST and the four-switch solution

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At the beginning and end of every Daylight Saving* Time period, I would get annoyed at my bedside clock. Why, I wondered, wasn't it built with a handy switch to toggle it between Standard Time and DST? That would be so convenient! But instead, I had to manually set it ahead an hour in the spring and back again in the fall, which required winding it through 60 minutes because it didn't have an hour button. (At least it could go in two directions, so I could back up in case I overshot.)

A year or so ago, I bought a new clock, with a feature called Insta-Set. When you first plug it in, it automatically sets itself. (Apparently it gets the current time info from a radio signal from somewhere.) All you have to do is set a switch to tell it what time zone you're in (only 4 options available: Pacific, Mountain, Central and Eastern. Sorry, Alaska, Hawaii, and rest of the world.) and tell it whether your area observes DST (good news for Arizona and Indiana!) and it resets itself automatically! I never need touch it again!

But then Congress voted to change the start and end dates of DST. As far as I can tell, there's no way to reprogram the clock with the new dates. So last Saturday night, my snazzy self-setting clock failed to reset itself. (Cue the crazy reporter from The Daily Show: "NOOOOOO!") So what do I do now? Throw it away and hope I can find a new one programmed with the new dates?

The immediate solution was simple enough: I've temporarily set the time zone switch to Eastern time, and then I'll have to set it back to Central time in three weeks. Oh yeah, and when DST ends, I'll have to set it to Mountain time for one week. A bit annoying, but flipping a switch four times a year definitely beats having to set the clock by hand twice a year. So, not enough reason to get rid of the clock. (Besides, there's the possibility Congress may go back to the previous dates later on, and if so my clock will be perfect again. :} )



*Usage tip: It's "Daylight Saving Time". Not 'Savings', because the phrase is not the name of a bank.

Current Music: Barenaked Ladies - Next Time

Comments:

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From:bassfingers
Date:March 13th, 2007 01:20 am (UTC)
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Ah, but what if it were a bank. A bank which was profiting on the interest accumulated by invested time?
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From:kinkyturtle
Date:March 13th, 2007 01:30 am (UTC)
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Its employees would be living on borrowed time.
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From:klepsydra
Date:March 13th, 2007 07:37 pm (UTC)
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Shades of F Anstey's "Tourmalin's Time Cheques"...
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From:wbwolf
Date:March 13th, 2007 01:30 am (UTC)
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I'm surprised that your clock didn't reset automatically. Our atomic clock (which, like yours) gets it's synchronization signal from Ft. Collins, CO and it correctly switched to DST without issue. My VCR I suspect checks the time signal coming from the cable company, so that was set correctly. Try changing it back to CST and see if it picks up CDT properly. Otherwise, the clock is not looking correctly at the DST flag in the signal.
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From:zorinlynx
Date:March 13th, 2007 02:32 am (UTC)
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The time signal from Ft. Collins, CO contains a bit that specifies whether DST is currently active or not. There may be a switch on it that turns DST on and off; look carefully. It's usually hidden in a really out of the way place like inside the battery compartment, or 20 miles below the surface of the earth in a safe labelled "No DST switch in here".

If such a switch doesn't exist, there are two posibilities:

1) The radio clock chipset doesn't implement the DST bit, and instead depends on the calendar date, which is an incorrect implementation according to the NIST folks, or

2) It does implement the DST bit, but the cheap bastards that designed it didn't put the switch in. So you'll have to find the data sheet on whatever radio clock chip they used, and manually connect or disconnect the appropriate pins.

Either way, good luck, and I hope you can fix it or find a clock that implements the NIST WWVB clock standard correctly.

-your friendly neighborhood geekylynx
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From:kinkyturtle
Date:March 13th, 2007 02:52 am (UTC)
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Well, I'll see what happens in three weeks.
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From:akseawolf
Date:March 13th, 2007 03:36 am (UTC)
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I recently bought a new alarm clock that automatically sets itself to the WWV signal. All I have to do is specify which timezone I am in. I just happened to be up when DST started this year and was a little surprised the time didn't change right away.

The clock has a button to force it to resync with with WWV signal, so I pressed that and a few minutes later it displayed the correct time. I figure if I hadn't forced the update it would have done it the next night on its own.
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From:palabrajot
Date:March 13th, 2007 07:53 am (UTC)
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I have three atomic-synced clocks in the house, (unless you count the clocks which synchronize indirectly, like the computers,) and of those, my clock radio chose to misbehave. I pulled its battery, so it'd have to reacquire the signal from Colorado. That settled its hash. Should work for you, too!
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From:kinkyturtle
Date:March 13th, 2007 09:12 am (UTC)
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I tried that just now. It didn't work. After I got everything hooked up and plugged in again, the clock thought it was 11:00. I had a look at the manual, and in fact there's no mention whatsoever of using a radio signal. Indeed, one section of the manual says:

"Insta-Time Incorrect:
If for some reason the Insta-Set time is incorrect or lost, press and hold the ALARM SET button for 5-7 seconds, and the year digit will begin to blink, then press the + or - button to set the year. Press the ALARM SET button again to set the month & date by pressing the + or - button. Press the ALARM SET button again to set the hour (be sure the AM/PM is correct), again to set minute, and once more to secure all in the memory.

No Time Displayed When Plugged into the AC Power:
If the display is blank when plugged into the AC outlet, open the button cell battery compartment and press reset button. In a few seconds, the display will be ON, and show 12:00.
(It showed 11:00 for me because I tried setting the switch back to Central.) Now repeat the procedure to set the real time memory above. After you have completed the time setting procedure, insert the Insta-Set battery (lithium button cell) and the time will be automatically stored in the clock."

In other words, as far as I can tell, this clock used the radio signal once to set itself when I first bought it, and then NEVER AGAIN, and if it needs resetting, I have to do it manually ANYWAY.

OK, I give up, where'd you get your clock?
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From:palabrajot
Date:March 14th, 2007 12:01 am (UTC)
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Well, mine's an Emerson, but I actually got it years before atomic sync was as commonplace as it is now, out of a clearance endcap at WalMart. My wall clocks are more recent but use the same principle, and they didn't seem to miss a beat.

I dunno how this 'InstaTime' business should be any different, though my alarm clock doesn't seem to concern itself with a year, or a DST switch. I'm surprised yours didn't reboot with the right time! Maybe the manufacturer has some support options; even if popping the battery out and pulling the plug worked, that doesn't sound like a huge improvement over moving the hour ahead by hand.
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From:kinkyturtle
Date:March 14th, 2007 12:35 am (UTC)
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I'm beginning to suspect this clock doesn't use a radio signal at all. My guess is, it gets set at the factory and runs (without displaying) on its little button battery until you buy it, then it tells you to plug it in and put a 9-volt battery into it, and the fact that it has three separate power sources is what keeps you from having to set it.

That's just speculation, of course, based on observing its behavior, and finding no mention whatsoever of any radio time signal in its manual.
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From:typographer
Date:March 13th, 2007 07:38 pm (UTC)
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Hmmmmmm, ours reset itself just fine.
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From:thecanuckguy
Date:March 13th, 2007 11:18 pm (UTC)
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A very ingenious plan! I was prepared to do something like that if my computer didn't behave correctly, but it did (it's relatively new, I think it was made after the Decree from On High, so it's safe).

My VCR (which is rather old as technology goes) automatically changes for DST, but not this time. I'm tempted to wait the three weeks (as it doesn't record right any more, I dont' have to worry about it for that), but I also could try resetting the clock (you can get the time automatically from channel 3 (no, doesn't have to do which is what is actually on channel 3, in my case PBS, but just channel 3 in general apparently carries a time signal along with, in my case, seldom watched TV and Britcoms))
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