[CentOS] tzdata, Greenwich zone: URGENT!

Guy Boisvert boisvert.guy at videotron.ca
Tue Jun 3 16:03:44 UTC 2008

Anne Wilson wrote:
> On Tuesday 03 June 2008 14:57:29 Karanbir Singh wrote:
>> Guy Boisvert wrote:
>>> Hi!
>>> It appears that there have been some changes to tzdata recently. We
>>> run an application that needs the server to stay at GMT. Previously, we
>>> used the Casablanca timezone but now there seems to be a 1 hour
>>> difference to GMT. I checked the London zone and they seem to change
>>> time too.
>> Looks like you were never on GMT / UTC - but on British Time, Which in
>> the summer is one hour off GMT
> Where/how is the system clock set?  My server appears to have the system clock 
> on GMT/UTC and KDE on British Time.
> Anne


	Thanks for all the fast responses!  I didn't know about the internals 
of the tzdata, the symlinks and the potential problems that Rick 
reported.  So finally, before the 1st response arrived from the list, i 
decided to do a "brute force" downgrade.

I downloaded the previous CentOS tzdata file from:


and did an rpm -ivh --force tzdata-2007k-2.el4.noarch.rpm

	I rebooted the server and everything went ok!  I didn't have the time 
to explain my case but for the sake of completeness, here it is:

1) Our application is for TV broadcasting.  We have a complete in-house 
developped automatic broadcasting system.

2) We have two players (1 active, 1 standby) that run on Windows 2000 
Server platform.  There are 3 deamons: Copy service (from the big 
multi-terabyte library to local "cache" of 200 gigs), Broadcaster 
(playlist maker) and Player.  The former 2 services read data from 
PostgreSQL database on CentOS x64 4.6.  As is said, the Broadcaster 
service read from the database and make the playlist then send it to the 
player.  Copier make check what it needs locally and act accrodingly. 
It managed a kind of big local cache.

3) The broadcast schedule is entered with a JAVA application that writes 
the time and date in GMT/UTC time in the database.  The JAVA application 
knows the local time and the offset and write accordingly, adding the 
amount of time required (we are in Montreal so it's GMT-4 or GMT-5) to 
"reach" GMT+0.

4) The database servers have always been in Casablanca zone and until 
today, it seems that it was never changing time.  1st of june, tzdata 
was updated by a yum update and since then, it was only a question of 
time before we'de be offset.  Playlists are looked up and made for 36 
hours so today was panic day!

5) Stumbling across the problem, i read many strange things while 
Googling, related to what Rick said in his post to the list: localtime 
file, symlinks, etc.  I was kinda lost!

Practically, as i said, i tried to find the GMT zone doing a 
system-config-date to no avail... I was shocked!  We shouldn't be the 
only one to have this need!

So, as i decode from what i received in response to my initial post, and 
correct me if i'm wrong, all that does system-config-date is to copy a 
file from /usr/share/zoneinfo/... into /etc/localtime ? (and maybe set a 
couple of symlinks?).

And if i do what Marcelo said:

cp  /usr/share/zoneinfo/right/Etc/GMT-0 /etc/localtime

am i cleared from future updates / changes in timezones?  I simply want 
the server to stay at GMT+0 and never change timezone.

I'm waiting for advice from experts!

And would it be possible to include "GMT+0" in system-update-date ? 
What is strange on top of all that is that the time of the schedule 
seems to be stored on the database relative to the local time of the 
server...  I'll have that checked by the programmers!

Many thanks to Marcelo, Rick, Karambir & Anne!

Guy Boisvert, ing.
IngTegration inc.

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