Timezone info

A.Fadyushin at it-centre.ru A.Fadyushin at it-centre.ru
Fri Oct 28 13:53:37 UTC 2005


The rules for time changes are described in zoneinfo files. So, if you
use the correct link '/etc/localtime' and that link points to the
up-to-date file (i.e. the file /usr/share/zoneinfo/Europe/London
contains officially declared time change rules which is currently in
force) your boxes will change the time exactly at the moment set in
zoneinfo files. If zoneinfo file contains correct rules it will be the
same moment as set by the government. Therefore, you will not have any
problems with the time change.

Also, you do not need to reboot the system for the change to take
effect. The internal clock in the Linux kernel always uses UTC,
regardless of tile zone. The localtime is then produced from the UTC on
the proccesses' requests in accordance with time zone information (e.g.
from /etc/localtime). At the moment of time change the kernel clock will
not be changed, only the rules for computation of local time will be
changed.

Alexey Fadyushin.
Brainbench MVP for Linux.
http://www.brainbench.com


> -----Original Message-----
> From: redhat-list-bounces at redhat.com [mailto:redhat-list-
> bounces at redhat.com] On Behalf Of Lunt, Nick
> Sent: Friday, October 28, 2005 2:24 PM
> To: Redhat (E-mail)
> Subject: Timezone info
> 
> Hi folks,
> 
> This Sunday in the UK the time will be going backwards one hour. I
need to
> know if I can tell the system when to make this change or how I can
find
> out when this change is scheduled for.
> 
> All our boxes use a local timeserver which punts out the UTC time and
our
> linux boxes convert that into the localtime for the box.
> 
> Here's some info from one of my boxes
> 
> # date
> Fri Oct 28 11:18:27 BST 2005
> # date -u
> Fri Oct 28 10:18:29 UTC 2005
> 
> Our /etc/localtime is pointing to /usr/share/zoneinfo/Europe/London.
> After the time change on Sunday `date` and `date -u` will output the
same
> time (I hope ;)
> 
> Can anyone give me any pointers on finding out when/how the boxes will
go
> back an hour please ?
> 
> It seems that the machine will only pick up the new time after a
reboot  -
> can anyone confirm this ?
> 
> I've tried googling with not much luck.
> I've also browsed the archives for last year around October but didn't
see
> anything there either.
> 
> Cheers
> Nick .
> 
> 
> 
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