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GPS, daylight savings time, and cars

With this morning's semi-annual changing of the clock for Daylight Savings Time (DST), I'm once again left to ponder...why, in this era of GPS-equipped automobiles, do I have to manually set the clock in my car? We had, until very recently (we sold one), three cars with factory GPS units. Of those three, only one uses the GPS signal to set the car's clock. In the other two vehicles, we have to manually adjust the clock, even though an extremely accurate time and date signal is one of the features of the GPS satellites.

So my car knows the date, and it knows the correct time...so why can't it figure out that DST has started or ended?

Things have definitely improved over the last 30 years, though--today, we had only a handful of clocks to change. In addition to one of the cars, there were a couple of televisions (another device that seems to me should be capable of changing its own clock), our microwave, and a few assorted clock radios and wall clocks. But most of the clocks we own synchronize automatically with a time signal, so they were correct when I woke up this morning. The computers, of course, handle the change seamlessly. (The fact that I stopped wearing a wrist watch a few years ago also helps; I have ten or so sitting in a drawer somewhere, but I no longer bother to set them.)

I'm not sure I'll live long enough to see a DST start/stop day where I don't need to manually set a clock...but I'm hoping I do!

7 Comments

  1. I'm sure there's someone out there more knowledgeable than I am about this - but I'd suspect the GPS satellites are all on UTC ("Coordinated Universal Time" - translated from the French Temps Universel Coordonné, hence the acronym.. thank you wikipedia!).

    So your GPS units get a very accurate measure of time, but you have to tell them what time zone you are in, so they can convert. Unless you've updated the software since the DST period changed, the unit will have no clue.

    Remember that the translation of GPS data to location occurs inside your GPS unit, not at the satellite level - the satellite doesn't really have a clue where your signal came from necessarily.

  2. In the one car that does set its clock automatically, we didn't have to do anything to tell it where we were -- given it's a GPS, it can figure out where it is, right? So in that car, at least, the car's GPS unit can talk to the clock. In the others, it seems it's an add-on, and isn't wired into the system.

    Offline, a friend came up with an explanation that also makes some sense: because most cars feature GPS as an option, it would take extra time, money, and effort to wire and program a connection between the GPS and the stock clock (which will be found in all models). So perhaps it's simply a money issue...

    -rob.

  3. Personally, I hope to live long enough to see the end of daylight savings time. That's the other way of solving these clock problems.

  4. I'm frustrated by this too, and I haven't followed auto technology lately. But I remember the joke about Microsoft that if MS designed cars you'd have to stop about three times a day and reboot, no matter where you were. This was in response to a Bill Gates comment: http://homepage.eircom.net/~nobyrne/ms-cars.htm

    Cars are much more reliable than computers. We can argue that, but spinning beach balls at 70 mph are undesirable to say the least.

    I believe the auto manufacturers have not interconnected the computers on the cars because of the reliability issues. If you remember Mercedes Benz and other high end car makers had severe functioning and reliability problems because they got carried away with fancy computer based functioning.

    So adding to Rob's comment on Rob's article, it's money and the effort to insure reliability.

    As a final comment, our iPhones had a hard time keeping the time correct on a recent drive in the Owens Valley (east of the Sierra Nevada). They kept jumping from PST (correct) to CST, yes two hours off.

  5. GPS does use UTC time, but when dst starts is programmed into the DVD disc. With the change instituted last year as to when dst starts, my car does not update the time until the old dates for dst are reached. Answer is to get a new DVD, but they usually want over $100 for updates

  6. I do not want to have a robot-like life so I do many things manual, few seconds to set your clock will remind you the worth of time.

  7. Here in Arizona we don't change our time (except for one Indian reservation). BUT...I still have the Daylight Saving Time issue with one alarm clock. It doesn't allow you to turn off DST!!

    I grew up in Michigan and my room had a window facing west. It was tough, in my grade school years, going to bed at 8pm and for two-and-a-half hours watching the sun set.

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