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Re: Time quandry when dual boot with WinXP Pro

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On Fri 21 Oct 2016 at 14:28:26 (+0100), Darac Marjal wrote:
> On Fri, Oct 21, 2016 at 08:09:38AM -0500, Richard Owlett wrote:
> >I'm creating a preseed.cfg file for installing Debian 8.6 in a
> >dual-boot enviroment with some version of MS Windows. There are
> >two distinct use cases:
> >  [snipped]
> 
> If you're not using NTP to provide your time, then, at boot, the
> operating system will query the "hardware clock" to see what time it
> is.  As the hardware clock can drift, operating systems will also
> set the hardware clock to match the "system clock" at shutdown time
> (the system clock is the time that the operating system is using).
> 
> The problem comes that there is no way for the hardware clock
> (HWClock) to report what timezone it was set to. There are basically
> two options here:
> 
> 1. The HWClock is set to "Local Time". In this case, the operating
> system sees "12:23" as being "12:23 GMT" or "12:23 CST" or whatever
> and attempts no translation of the clock.
> 
> 2. The HWClock is set to "Universal Time" (which is a
> non-geographical datum time zone, with no daylight changes). In this
> case, the operating system sees "12:23" as ONLY being "12:23 UTC"
> and translates that into the local time zone by adding or
> subtracting hours appropriately.
> 
> If you only have one operating system on your machine, either of
> these methods is fine. If you have TWO (or more) operating systems,
> though, then they SHOULD agree on what the time in the HWClock
> represents. If Windows thinks it's local time, but Debian thinks
> it's UTC, then you'll see five-hour shifts each time you boot.
> 
> You've already found the setting in Debian, I see, so you probably
> want to check it tallies with what Windows is using. For that, look
> at the Registry Key HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal.
> If this is 1, then the HWClock is using UTC; if it is 0, then the
> HWClock is set to local time.

So what happens with the scenario:

. No NTP connection,
. Hardware clock running on Local Time,
. Two or more OSes that know these two facts.

. Neither OS was running when Civil Time changed to/from DST,
. After the time changed, one OS has run, updating the Local Time to match Civil Time,
. Another OS is just being booted up.

What Local Time will eventually be displayed by this system?

Cheers,
David.

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Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 15:20 +0200
  Re: Time quandry when dual boot with WinXP Pro Darac Marjal <mailinglist@darac.org.uk> - 2016-10-21 15:30 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 16:50 +0200
    Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-21 17:10 +0200
      Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-21 19:50 +0200
        Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-22 17:10 +0200
          Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-22 17:10 +0200
          Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-22 17:50 +0200
            Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-23 04:50 +0200
  Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 15:40 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 16:30 +0200
      Re: Time quandry when dual boot with WinXP Pro Doug <dmcgarrett@optonline.net> - 2016-10-21 18:50 +0200
        Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 20:20 +0200
          Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 21:20 +0200
      Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 21:20 +0200
        Re: Time quandry when dual boot with WinXP Pro tomas@tuxteam.de - 2016-10-21 21:30 +0200
          Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 22:20 +0200
            Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 22:40 +0200
  Re: Time quandry when dual boot with WinXP Pro Stefan Monnier <monnier@iro.umontreal.ca> - 2016-10-22 22:10 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-22 22:20 +0200
      Re: Time quandry when dual boot with WinXP Pro Stefan Monnier <monnier@iro.umontreal.ca> - 2016-10-22 22:20 +0200
        [REPOST] Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-25 14:20 +0200
        Side effects of specifying use of NTP on installation???? - was [Re:  Time quandry when dual boot with WinXP Pro] Richard Owlett <rowlett@cloud85.net> - 2016-10-25 14:20 +0200
  Re: Time quandry when dual boot with WinXP Pro Lisi Reisz <lisi.reisz@gmail.com> - 2016-10-29 16:50 +0200
    Re: Time quandry when dual boot with WinXP Pro Felix Miata <mrmazda@earthlink.net> - 2016-10-29 17:30 +0200
      Re: Time quandry when dual boot with WinXP Pro Lisi Reisz <lisi.reisz@gmail.com> - 2016-10-29 18:20 +0200

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