Avoid Going into DST Without Changing Timezone

paperbagperson · 03-11-2016, 02:20 PM

According to a nice zdump, my server will be going into DST time this Sunday

Code:

# zdump -v /etc/localtime | grep 2016
/etc/localtime  Sun Mar 13 06:59:59 2016 UTC = Sun Mar 13 01:59:59 2016 EST isdst=0 gmtoff=-18000
/etc/localtime  Sun Mar 13 07:00:00 2016 UTC = Sun Mar 13 03:00:00 2016 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  6 05:59:59 2016 UTC = Sun Nov  6 01:59:59 2016 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  6 06:00:00 2016 UTC = Sun Nov  6 01:00:00 2016 EST isdst=0 gmtoff=-18000

Is there a way for me to edit some file so that the server doesn't change the time this Sunday without changing the server's timezone?

sundialsvcs · 03-11-2016, 02:30 PM

The answer is: "yes."

Any time-zone file (".tz file") can be selected, and this file will specify among other things the dates of a daylight-time ("DST") shift, if any, and obscurities like "leap seconds."

Several time-zone files are readily available for places that ordinarily follow different customs. For example, Arizona (USA) does not observe DST, so there's a standard file for "Phoenix." But the Navajo nation, within Arizona, does observe DST, so they might use the file for "Denver."

You can tell your system to use any time-zone file you wish ... or, create one of your own.

TZ files are also good for historical dates!

The time-zone files not only remember "DST rules for the present day," but also the periods of time in the past when other rules applied, so that an absolute-time (UTC) can still be correctly converted to what is ... or, as the case may be ... would have been, the correct local interpretation of "that point in time."

For a good reference, see:

List of time zones https://en.wikipedia.org/wiki/List_o...ase_time_zones
Time-zone database https://en.wikipedia.org/wiki/Tz_database
Daylight time (computing) https://en.wikipedia.org/wiki/Daylig...time#Computing

suicidaleggroll · 03-11-2016, 02:31 PM

I think you would have to edit the dates of the DST jump for your tz file, but why would you want to do that? The only thing that will change are scheduled jobs through cron and the times that get printed out when you run an ls or date (without the -u flag), nothing else should be affected AFAIK.

paperbagperson · 03-11-2016, 02:48 PM

Quote:

Originally Posted by sundialsvcs

You can tell your system to use any time-zone file you wish ... or, create one of your own.

How would I go about creating my own/editing a .tz file?

michaelk · 03-11-2016, 04:47 PM

Never played with the tz database but you would need to install the zic compiler as well as the source files. I know it is not what you wanted but you could change to a fixed time zone i.e. GMT-5.

https://www.iana.org/time-zones/repository/tz-link.html