Daylight savings time

Discussion in 'Apple' started by Isaac Wingfield, Aug 24, 2005.

  1. Well, it looks like the starting and ending dates of DST might change.

    I'm pretty sure that in some very ancient incarnation of Mac OS, I knew
    how to change those dates -- seens like it changed once before,
    temporarily? Or something.

    Anyway, I have a cluster of Macs, all running OS 9, to take care of, and
    I have no idea where to look to change the start and end dates of DST.

    Any suggestions?

    thanks, Isaac
    Isaac Wingfield, Aug 24, 2005
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  2. IIRC, the settings are in the 'Date & Time' control panel. I 'think'
    there is a DST checkbox there. Eventually, you will probably have to lie
    to the computer about what time it is when the US gets the two hour
    boost in DST, but that won't be this year.
    I purely speculate that the DST checkbox hops and falls one hour.

    Leonard Blaisdell, Aug 24, 2005
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  3. Isaac Wingfield

    Geoff Walker Guest

    You should check the Use a Network Time Server box in the Date & Time
    control panel - that will take care of it automatically.

    Geoff Walker, Aug 24, 2005
  4. No, NTP transfers the exact universal time, it is up to the computer to adjust
    this "exact" time to its local time, daylight savings time or whatever.

    There is a shareware NetworkTime where you may specify your own DST rules. Use
    that one and don't let Apple's control panel do the job.

    Christoph Gartmann

    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Postfach 1169 Internet: [email protected] dot mpg dot de
    D-79011 Freiburg, Germany
    Christoph Gartmann, Aug 24, 2005
  5. Well, I suspect there will be an update to the OS (and all OS's that
    are supported to fix this).

    Since MacOS is Darwin-based, it may well use the Unix timezone info
    which can be found in /usr/share/zoneinfo.

    These are compiled binaries, so see:

    man zic
    man tzfile
    man tzset

    in a command prompt.

    Personally, I'd wait - there will be an update from Apple.

    Stephen M. Adams, Aug 24, 2005
  6. You didn't read the original post carefully enough. We are speaking about
    OS 9, so I wouldn't expect anything from Apple.

    Christoph Gartmann

    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Postfach 1169 Internet: [email protected] dot mpg dot de
    D-79011 Freiburg, Germany
    Christoph Gartmann, Aug 24, 2005
  7. But it won't be possible to use those tools to update the TZ data until
    updated information is available. Mac OS X's time zone system is the
    same as in BSD, which in turn is based on the data available from
    <> (actual data is at
    <>). In the past the people behind this
    project have been very good about keeping it up to date, though it
    doesn't appear they've updated it for future US DST rules yet.
    Certainly. However it remains to be seen what versions of Mac OS X they
    issue an update for. If they don't cover, for example, 10.1.x, it
    wouldn't be too hard for someone to create an updater for these Macs. I
    might do it myself, but since the new rules don't take effect for a
    while, there's no rush.
    Tom Harrington, Aug 24, 2005
  8. but since the new rules don't take effect for a
    Oh, nooooooo! It'll be another Y2K DISASTER!!!!! Everything put off till
    the last minute, my refrigerator will crash, trains will collide, and all
    power will cease.

    Time to start hoarding lawyers, guns, and money.
    Phil Stripling, Aug 24, 2005
  9. Move to Arizona, Hawaii, Alaska, or western Indiana; there's no DST
    there, so it won't be an issue. <g>
    Michelle Steiner, Aug 24, 2005
  10. Isaac Wingfield

    Dave Seaman Guest

    Dave Seaman, Aug 25, 2005
  11. IIRC, prior to OS X you had to check or uncheck "Daylight Savings Time"
    in the Date & Time control panel manually. I used a shareware control
    panel called "Daylight!" that automated this on the appropriate days.

    But I could be remembering even further back, maybe that was OS 8, and
    OS 9 handled it automatically itself.
    Barry Margolin, Aug 25, 2005
    Tom Harrington, Aug 25, 2005
  13. No, it will not. An NTP server cannot know what time zone you are in.
    You have to tell your computer how many hours to offset the GMT that all
    NTP servers deliver. Then you have to tell your machine when DST starts
    and stops. If those dates change, you have to tell your computer that,

    Isaac Wingfield, Aug 25, 2005
  14. Isaac Wingfield

    Geoff Walker Guest

    Not right. And I know because I've had to do it before - let me explain.

    In 2000, daylight saving was introduced in New South Wales a month or so
    earlier than normal as a one-off on account of the Sydney Olympics. But
    the network time server I was using at the time ( didn't
    switch to daylight saving on the earlier-than-normal commencement date,
    even with the Set Daylight-Saving Time Automatically box checked. So I
    ferreted around and found some Australian-based network time servers.
    These included, and
    I set my Date & Time control panel to one of those (don't remember which
    - I've purchased a newer Mac since then) and my time went straight to
    the correct daylight saving time.

    In other words, changing the network time server changed the time shown
    by my computer. Therefore the change must have come from the network
    time server itself. The conclusion is therefore that the network time
    servers can have knowledge of the daylight savings time for the various
    time zone/geographic combinations.

    Geoff Walker, Aug 25, 2005
  15. Isaac Wingfield

    Jeff Wiseman Guest

    You forgot your MREs (Macs Ready for Eternity)
    Jeff Wiseman, Aug 25, 2005
  16. Nah, with that golden trio, you don't _need_ MREs. You can get all you want
    later. :->
    Phil Stripling, Aug 25, 2005
  17. I can't speak to the foibles of individual time sservers, but I don't
    think you can find that in RFC 1305, which is the "spec" for NTP.

    In particular, there are no fields available in the message that is
    passed from the server to you for specifying the location of the server,
    or its offset from GMT, or even whether DST is in effect at the server's

    And even IF the network time server could tell you where it was, you'd
    still have to tell yout computer where *it* was.

    Isaac Wingfield, Aug 26, 2005
  18. Isaac Wingfield

    Geoff Walker Guest

    I didn't change my timezone definition!

    As Sherlock Holmes said to Dr Watson, "When you've eliminated the
    impossible, what remains, no matter how improbable, must be the truth."

    Therefore, assuming what you say about NTP is correct, and I know that
    what I said above about the different network time servers resulting in
    different DST outcomes in 2000 was fact, the truth must be that Macs
    aren't restricted to NTP.

    A little further ferreting around reveals that there are a number of
    time protocols in addition to NTP, e.g.
    reveals the existence of Daytime Protocol (RFC 867) and Time Protocol
    (RFC 868).

    Daytime Protocol is said to be "... widely used by small computers ..."
    and contains code indicating whether Standard Time or DST is in effect
    in the US.

    I conclude that the Australiian network time server I ended up on must
    have worked on a protocol akin to Daytime Protocol containing relevant
    code for the various time zones/geographic combinations in the
    Australian states and territories to give me the DST result I wanted.

    Geoff Walker, Aug 27, 2005
  19. Isaac Wingfield

    David Magda Guest

    Why would you want to specifiy your own rules?
    David Magda, Aug 28, 2005
  20. The original poster has the Macs running under OS9. There is no possibility to
    modify the DST rules under OS9. So when they change in reality you rely on
    Apple. But I don't expect Apple to provide a software update for OS9.

    Christoph Gartmann

    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Postfach 1169 Internet: [email protected] dot mpg dot de
    D-79011 Freiburg, Germany
    Christoph Gartmann, Aug 28, 2005
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