[nSLUG] DST & tzdata

D G Teed donald.teed at gmail.com
Sun Mar 4 20:54:55 AST 2007


Hi,

The DST solution for our zone in Olsen format requires running the
"backward" part of the zones to make links.  That is why it appears
to have missing stuff.

Here is a solution based on what I summarized for the sun-managers
mailing list.  Of course you need to change the "c" after "2007" into
whatever revision is on the .gov site now,
if the link we refer to no longer works:

Download data from:
ftp://elsie.nci.nih.gov/pub/tzdata2007c.tar.gz<ftp://elsie.nci.nih.gov/pub/tzdata2007a.tar.gz>

gunzip -c tzdata2007c.tar.gz | tar xf -

for i in africa antarctica asia australasia etcetera europe northamerica
pacificnew southamerica backward
do
  echo $i
  zic $i
done

backward has to be last in that list.

This handles /etc/localtime pointing to a TZ like "Canada/Halifax"
or "America/Halifax".  If your TZ is a POSIX style timezone,
like "AST5ADT" (unlikely), then you need a libc update to handle
that change.

If Slackware isn't providing these sorts of updates, you might as well
be running Solaris 6.  It isn't supported by it's maker either.

Debian and most other Linux users don't have to fret about this, as
the changes for our zone came down in updates a few months back.

--Donald

On 3/4/07, George N. White III <gnwiii at gmail.com> wrote:
>
> On 3/4/07, Mike <mspencer at tallships.ca> wrote:
>
> > Slackware seems not to have a patch or equivalent for the new DST
> > rules that GloboCop has ordered.  We're apparently being sucked
> > into the propwash.
> >
> > So I fetched the tzdata files from:
> >
> >    ftp://elsie.nci.nih.gov/pub/tzcode2007c.tar.gz
> >
> > dated Mon Feb 26. Therein I note that the rules for America/Halifax
> > haven't been updated to the new dates and there is no Zone... line for
> > AST/ADT.  I think I understand from inference and the  zic(8) manpage
> > how to fix things up but...
>
> The files are tricky to read.  Look for the lines:
>
> Rule    Canada  2007    max     -       Mar     Sun>=8  2:00    1:00    D
> Rule    Canada  2007    max     -       Nov     Sun>=1  2:00    0       S
>
> and note that America/Halifax is most recently (since 1974) set to
> Canada.  After you have installed the files,
>
> $ zdump -v America/Halifax | grep 2007
> America/Halifax  Sun Mar 11 05:59:59 2007 UTC = Sun Mar 11 01:59:59
> 2007 AST isdst=0 gmtoff=-14400
> America/Halifax  Sun Mar 11 06:00:00 2007 UTC = Sun Mar 11 03:00:00
> 2007 ADT isdst=1 gmtoff=-10800
> America/Halifax  Sun Nov  4 04:59:59 2007 UTC = Sun Nov  4 01:59:59
> 2007 ADT isdst=1 gmtoff=-10800
> America/Halifax  Sun Nov  4 05:00:00 2007 UTC = Sun Nov  4 01:00:00
> 2007 AST isdst=0 gmtoff=-14400
>
> > Before I do that, does anybody know of any gotchas?  Is there an
> > authoritative Canadian site that has updated tzdata files for Canadian
> > zones?
> >
> > More technical yet: Is there any reason why I can't compile just the
> > zoneinfo file for America/Halifax and put the binary into the
> > canonical zoneinfo directory without doing the other zone files?  My
> > own machine isn't a server and never moves out of the AST/ADT
> > zone. Does anything important regularly use the zoneinfo files for
> > *non-local* zones?  F'rgzample, if I get ntp running using a server in
> > Boston or Ontario, will ntp reference my local zoneinfo files for for
> > EST/ADT?
>
> Do you keep your hardware clock (the one that runs from battery while
> the system is off) on UTC?  ntp should not touch the tzdata stuff --
> normally it is only concerned with UTC, but if you keep the hardware
> clock on localtime (e.g., in order to dual boot Windows), tzdata would
> be used to translate to/from UTC when booting and shutting down to
> read/set the hardware clock.
>
> --
> George N. White III <aa056 at chebucto.ns.ca>
> Head of St. Margarets Bay, Nova Scotia
>
>
>
> _______________________________________________
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>
> 
>
>


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