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Thread: Daylight Savings Time

  1. #1
    JTB
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    Daylight Savings Time

    Any explanation? What is it and why it changes the shadows?
    Thanks...not much help found.

  2. #2
    Senior Member rkitect's Avatar
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    http://tinyurl.com/3lu59g2

    Should explain everything.

    It changes the shadows because man learned how to manipulate the thing it created! >_>

    Story Time:
    Some farmers in Kansas actually went and argued against continuing to support Daylight Savings Time in Kansas because they "didn't want an extra hour of sunlight to burn their crops"

    This is a true story heard through a friend (who is not known for his exaggerations).

  3. #3
    JTB
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    Thanks, I was trying to find something in Revit help.... Well, it is exactly what I knew it is... so I will use it for shadows...

  4. #4
    Senior Member rkitect's Avatar
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    It's meant to simulate the change in sun position during Daylight Savings time.

  5. #5
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    Unless you are in Arizona. They don't observe DST.

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    Quote Originally Posted by dzatto View Post
    Unless you are in Arizona. They don't observe DST.
    that's why I go there to golf...they get an extra hour of sunlight. Or, maybe an hour less, I'm confused now

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    Quote Originally Posted by Dave Jones View Post
    that's why I go there to golf...they get an extra hour of sunlight. Or, maybe an hour less, I'm confused now
    Well if you are under par, its an hour more. If you are over par, its an hour less because you want the round to end sooner. Lol

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    Administrator Ian.Kidston's Avatar
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    Hi All,
    I must say that I haven't checked if there has been any changes to this function since Nov09 when I had a major problem with using the Daylight Saving Function. Below is the first part of what ended up to be a longish thread on AUGI at the time.

    Motto of the story (as it was then), be very, very careful with this tick box.

    Hi All,

    In a current application before council, the officer noted that the 3pm shadow did not look correct and was probably closer to 2pm than 3pm.

    I went through and checked everything in the model - true north - shadow setting etc and all seemed OK.

    I was about to go into panic mode and fire off a support request when I thought to check if the tick box for daylight saving was activated. It was. Unchecking it brought everything back to display correctly.

    The info in the help on this is a bit ambiguous.

    It says: 4. If you want shadows to reflect daylight savings time for the specified location, select Automatically adjust clock for daylight savings changes.


    When I had read it before setting the daylight saving switch I had taken this to mean that Revit would adjust to daylight saving time much as the clocks within Windows do when you get to the appropriate date for which ever city you are in. It would appear that this isn't the case and this tick box simply moves the time frame one hour regardless of date when the shadows are set for.

    In Melbourne, we typically provide shadows for the equinox (22nd September) which is well before the daylight saving kicks in. Thus, because I had the "daylight saving" box ticked, Revit had indeed moved the shadows one hour and the 3pm shadows was in fact displaying a 2pm setting.

    Cheers,


    Ian


    Further Info:
    I have just checked the functionality in 2012. Exactly the same behavior as previously described. This tick box is VERY dangerous, and imo should never be used.
    Last edited by Ian.Kidston; May 30th, 2011 at 04:03 AM. Reason: Further info

  9. #9
    Forum Co-Founder Alfredo Medina's Avatar
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    Quote Originally Posted by Ian.Kidston View Post
    In a current application before council, the officer noted that the 3pm shadow did not look correct and was probably closer to 2pm than 3pm.
    ...
    I have just checked the functionality in 2012. Exactly the same behavior as previously described. This tick box is VERY dangerous, and imo should never be used.
    That council officer is dangerous, too. He has a very sharp sight!

    Very interesting observation. So the check mark does what it is supposed to do only in part. Because it does not verify if the current date is out of the summertime in that particular location. Maybe the programmers left that part out because it was too complicated to do, considering that daylight savings time observance depends not only on the date, the location, but also, on a decision of local authorities? So they left it up to the user to check if, for the chosen date and location, daylight savings should be considered or not. So, yes, use this with caution.

  10. #10
    Administrator Ian.Kidston's Avatar
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    Quote Originally Posted by Alfredo Medina View Post
    That council officer is dangerous, too. He has a very sharp sight!

    .
    Alf,

    You give them too much credit, at Melbourne's latitude of 37 degree south, the difference between 2pm and 3pm shadows is pretty obvious if one looks.

    There are two major problems with this tick box.

    Firstly, once we set up the location, rotate true north, we never actually do the calculations to confirm that the shadows are correct. Should we manually check them before they go out? Probably but, having previously, (several years ago), checked all the shadow generation against the calculated values for Melbourne, and found them all to be correct, there is no particular reason to suspect they could be inaccurate and manually recheck the shadows again.

    Secondly, it is a global tick box which changes every shadow in the model rather than an instance based control which would change the shadows only of which ever particular instance you had ticked. This is where it will catch people out. From time to time, usually when we are dealing with difficult neighbours, council will ask us to produce summer solstice shadow. Workflow - Duplicate an existing view - change the date - tick the daylight savings button (as late December is within the Daylight Saving Time) and off you go, blissfully unaware that every other shadow has been changed. End up at the Planning Tribunal with a $12,000 per day lawyer on the other side of the bench. Suddenly you are a rabbit in the spot light about to become roadkill.

    With it's current functionality, I cannot imagine any circumstance where one would be able to use it.

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