Clock/Time issues

[Matthew Saltzman]

On Mon, 25 Apr 2005, Charles Malespin wrote:

> I forgot to mention that I am running a dual boot with XP on the other
> side.  Does this mean that I cant use the UTC option?  Is there
> something else that I can do since I am using XP?  Thanks,
> Charles

You can set Linux to expect the hardware clock to contain local time 
(using system-config-date), but the switch back and forth between standard 
time and daylight time is a pain.  Linux only updates the hardware clock 
for daylight time if it is running when the switch is made.  Windows 
updates the first time it's booted after the switch whether Linux updated 
it or not.  In Windows, each user can set the update flag individually. 
On a multi-boot, multi-user system, chaos ensues when the changeover 
occurs.

I have a dual-boot FC/XP system.  I don't use the XP side much, so I did 
the following:

(1) Set up Linux so the hardware clock uses UTC and Linux uses my timezone 
(US Eastern).

(2) Set up Windows to use timezone GMT (GMT standard time is the same as 
UTC).

(3) Turn off daylight savings time auto-adjust for all Windows users.

(4) Live with the fact that Windows time is 4-5 hours later than local 
time.  If I want to know what time it is when in Windows, I look at my 
watch.


>
> On Mon, 2005-04-25 at 15:32 -0400, Deron Meranda wrote:
>> On 4/25/05, Bruno Wolff III <bruno at wolff.to> wrote:
>>> On Mon, Apr 25, 2005 at 11:51:59 -0500,
>>>   Charles Malespin <charles.malespin at gmail.com> wrote:
>>>> Hi all,
>>>>    I am running FC3 with the newest kernel 2.6.11 but am having some
>>>> clock issues.  Every time I boot up the clock is set back 5 hours from
>>>> what the actual time is.
>>>
>>> This is usually caused by the bios having the clock set to local time,
>>> but linux is assuming it is GMT.
>>>
>>> The right way to do this is to have the BIOS clock set to GMT, but I don't
>>> think this works well with Windows if you are dual booting the machine.
>>
>> Yes, you want the BIOS hardware clock to be set to UTC time.  The
>> only reason to ever leave the BIOS in "local" time is if you are
>> dual-booting with Windows which can not deal with timezones correctly.
>> As long as you're all Unix/Linux/BSD: hardware clock should always be UTC.
>>
>> The system-config-date GUI has a checkbox for "system clock uses UTC".
>> As well, you can just edit the config file /etc/sysconfig/clock and set the
>> UTC= variable to true
>>
>>    UTC=true
>>
>> then reboot.  Also you may want to set up NTP, or at least one-shot
>> set the clock with a command like following,
>>
>>    ntpdate 0.pool.ntp.org
>>
>
>
>

-- 
 		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs