irksome timezone question - dual boot laptop

[James Knott]

What is the correct way to have my time set so that both linux and
windows get it right and I can bounce between timezones as I travel.

Configure Windows so that it does not change the hardware clock.

which puts me half way to Japan!

So, how are things on Midway Island? ;-)

[phanisvara das]

On Thu, 11 Nov 2010 22:29:27 +0530, Greg Freemyer

What is the correct way to have my time set so that both linux and
windows get it right and I can bounce between timezones as I travel.

i remember reading, during install, that one shouldn't use UTC when also
running linux. by default the option is checked, i think. if it's checked
in your case, i'd try unchecking it.

[phanisvara das]

On Thu, 11 Nov 2010 23:05:48 +0530, phanisvara das

Post by phanisvara das
i remember reading, during install, that one shouldn't use UTC when also
running linux.

sorry, meant to say "...when also running windows."

[Rodney Baker]

All,
I have a dual-boot laptop I brought on trip from Eastern Standard Time
to Pacific Standard Time.
After getting to Pacific area I went into Yast and changed my timezone
appropriately and double checked it was setup to use ntp.
All was good, until yesterday I dual booted into Windows. I didn't
pay attention to the time it had, but now I'm back in openSUSE, my
clock is off by 4 hours which puts me half way to Japan!
What is the correct way to have my time set so that both linux and
windows get it right and I can bounce between timezones as I travel.
Thanks
Greg

Use NTP and set it to point to a public timeserver (e.g. pool.ntp.org).
Unfortunately Windows keeps it TZ variable in the registry so automatically
updating Windows' TZ variable via a bash script while running Linux is non-
trivial.

You could always do what I do - boot your Windows partition in VirtualBox from
Linux - that way the time is pretty much always in sync.

[James Knott]

Post by phanisvara das
i remember reading, during install, that one shouldn't use UTC when
also running linux. by default the option is checked, i think. if it's
checked in your case, i'd try unchecking it.

No. You shouldn't use UTC, if you're dual booting into Windows. Linux
handles UTC just fine. It's Windows that messes things up.

[Carlos E. R.]

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All,
I have a dual-boot laptop I brought on trip from Eastern Standard Time
to Pacific Standard Time.

Intersting problem.

After getting to Pacific area I went into Yast and changed my timezone
appropriately and double checked it was setup to use ntp.
All was good, until yesterday I dual booted into Windows. I didn't
pay attention to the time it had, but now I'm back in openSUSE, my
clock is off by 4 hours which puts me half way to Japan!
What is the correct way to have my time set so that both linux and
windows get it right and I can bounce between timezones as I travel.

The typical advice is to set cmos time to local time, so that Windows
doesn't have problems, because Linux can use both settings. But when you
change timezones, the cmos clock is changed several hours while the other
OS is off, and you will have problem regardless of what OS you boot first
and which later: the other one will see a time shift.

So when you travel and change the local timezone and double boot you have
to leave the cmos at UTC (which doesn't change), and tell windows that the
cmos clock is UTC. I understand that Windows-7 can do this, others might
not (I do not know which version started to allow this).

- --
Cheers,
Carlos E. R.
(from 11.2 x86_64 "Emerald" at Telcontar)

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[David C. Rankin]

What is the correct way to have my time set so that both linux and
windows get it right and I can bounce between timezones as I travel.

make sure SuSE is set to use local time *not* GMT. That is a must with dual-boot
boxes (or at least it was through vista). Win doesn't understand the hwclock set
to GMT so win will always be off by the tzoffset if you set Linux to use GMT.
--
David C. Rankin, J.D.,P.E.
Rankin Law Firm, PLLC
510 Ochiltree Street
Nacogdoches, Texas 75961
Telephone: [phone]
Facsimile: [phone]
www.rankinlawfirm.com

[David C. Rankin]

Post by David C. Rankin
make sure SuSE is set to use local time *not* GMT. That is a must with dual-boot
boxes (or at least it was through vista). Win doesn't understand the hwclock set
to GMT so win will always be off by the tzoffset if you set Linux to use GMT.

Err, replace GMT with UTC above (although they are the same for all practical
purposes, or for that matter, 0 zulu)
--
David C. Rankin, J.D.,P.E.
Rankin Law Firm, PLLC
510 Ochiltree Street
Nacogdoches, Texas 75961
Telephone: [phone]
Facsimile: [phone]
www.rankinlawfirm.com

[Carlos E. R.]

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Post by David C. Rankin

Post by David C. Rankin
make sure SuSE is set to use local time *not* GMT. That is a must with dual-boot
boxes (or at least it was through vista). Win doesn't understand the hwclock set
to GMT so win will always be off by the tzoffset if you set Linux to use GMT.

Err, replace GMT with UTC above (although they are the same for all practical
purposes, or for that matter, 0 zulu)

That setting will not work well if you change zones, because there is no
zone information in the cmos clock.

Think.

Europe. Cmos store local time. Fly to New York. Linux. You change the the
time zone, not the clock: it is automatic. The changed hour goes to the
cmos. Now you boot windows - but windows still thinks in European time,
and is off by 6 hours. So you also have to change it. And when you change
its time zone it will also change the time again.

As I understand, Windows 7 can use the cmos at utc. So I was told, I have
to find the setting.

- --
Cheers,
Carlos E. R.
(from 11.2 x86_64 "Emerald" at Telcontar)
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[James Knott]

The crazy part is that it seems the basic windows design calls for the
user to change their bios clock every time they change timezones.
That is just hard for me to believe.

That goes back to the DOS days, before portable or networked computers.
In fact, back in those days, a hardware clock was an option and not
built into the motherboard. Back then they were primarily worried about
file time & date and not much more. With Linux & Unix, GMT was used
from the start, perhaps because it was developed at a telecommunications
company, where GMT is commonly used.

[Carlos E. R.]

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So MS made a bad decision back when Bill Gates was still programming.

They made a lot more mistakes than that. ;-)
Incidentally, I worked at IBM Canada in the late 90's. In order to to my job
(3rd level OS/2 support), I had accounts set up on several different domains
across the country. When I logged into a domain in a different time zone, my
computer would change to the time for that time zone.

And some games, like the mentioned Flight Simulator. If you changed the
hour of the game, to simulate flying on different conditions, the hour and
date of the computer was changed accordingly.

- --
Cheers,
Carlos E. R.
(from 11.2 x86_64 "Emerald" at Telcontar)
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[James Knott]

So MS made a bad decision back when Bill Gates was still programming.

They made a lot more mistakes than that. ;-)

Incidentally, I worked at IBM Canada in the late 90's. In order to to
my job (3rd level OS/2 support), I had accounts set up on several
different domains across the country. When I logged into a domain in a
different time zone, my computer would change to the time for that time
zone.

[Carlos E. R.]

date and not much more.  With Linux & Unix, GMT was used from the start,
perhaps because it was developed at a telecommunications company, where GMT
is commonly used.

So MS made a bad decision back when Bill Gates was still programming.
They knew it was a bad decision the first time someone took a luggable
running DOS on a plane. Maybe 1983 or so.

Perhaps not, it was IBM.

The PC had to ask the user for the time every time it booted. Time zones
were not changed, you simply booted and typed the current hour. The
machine did not run for long, anyway, and time was unreliable. Using local
time was far easier than using UTC and timezones. Consider the OS had less
than 360 KiB of disk space, nobody thought that the machine would be such
a success and any design decision would have consequences farther away
than 5 years.

Including the decission to hire MS to do an OS! :-p

It really is not that hard to fix. Linux has had the "UTC / Local"
checkbox for the hardware clock as long as I can remember. And as far
as I know, it works reliably.

It is probably nearly impossible to change now, because any trivial change
affects many functions and third party software.


I don't think they see a problem with using local time, even if you
travel. You have to change the timezone anyway, the clock is adjusted
adequately, and on next boot it works fine. Only people double-booting to
linux have problems - so why would they care?


- --
Cheers,
Carlos E. R.
(from 11.2 x86_64 "Emerald" at Telcontar)