[lug] Disable daylight savings time

[Scott Herod]

On Sat, 10 Jul 2004, Gary Hodges wrote:

> I'm not generating any respones to this on a Debian newsgroup, so I
> thought I'd try here.  How can I disable daylight savings so the machine
> always operates in standard time?  I figured this would be an easy
> Google find, but it seems not.  
> 
> My problem is with the Pacific time zone.  I have some software that
> offers multiple selections for all the other times zones I have
> instruments in, one of which is always a place that doesn't follow
> daylight savings, e.g., Arizona(-7) and Indiana (-5).  I only have one
> choice for Pacific (-8), so all my data there are time stamped with
> local daylight time.  Setting the machine to local standard time would
> be an easy fix for me.
> 
> Gary
> 


Hi Gary,

Daylight savings time changes are encoded in files in 
/usr/share/zoneinfo/.  You can use zdump to print out the files in a 
readable format.  For example:

[bash]% zdump -v /usr/share/zoneinfo/US/Mountain
/usr/share/zoneinfo/US/Mountain  Fri Dec 13 20:45:52 1901 UTC = Fri Dec 13 
13:45:52 1901 MST isdst=0 gmtoff=-25200
/usr/share/zoneinfo/US/Mountain  Sat Dec 14 20:45:52 1901 UTC = Sat Dec 14 
13:45:52 1901 MST isdst=0 gmtoff=-25200
/usr/share/zoneinfo/US/Mountain  Sun Mar 31 08:59:59 1918 UTC = Sun Mar 31 
01:59:59 1918 MST isdst=0 gmtoff=-25200
/usr/share/zoneinfo/US/Mountain  Sun Mar 31 09:00:00 1918 UTC = Sun Mar 31 
03:00:00 1918 MDT isdst=1 gmtoff=-21600

(etc)

I think that you may want to use a timezone in the 
/usr/share/zoneinfo/Etc/ directory.  For example, check
zdump -v /usr/share/zoneinfo/Etc/GMT-8.  (That is PST right?)

Then once you have decided on a timezone file you can copy it to 
/etc/localtime.  For example, on my machine:

diff /etc/localtime /usr/share/zoneinfo/America/Denver

returns empty.

Be aware that every running process has static data containing the 
timezone info which cannot be updated.

Scott