Re: [PATCH] Fix: wrong offset for CET timezone

From: Robin Rosenberg <robin.rosenberg@dewire.com>
Date: Jun 27, 2014, 08:51 UTC
Message-ID: <339300321.129156.1403859105924.JavaMail.zimbra@dewire.com>
In-Reply-To: <CAF3z5=m5Ac5qWuXNXZaRqfDjbmt37qHjbj6YxkaE12VYsZegcg@mail.gmail.com>

----- Ursprungligt meddelande -----

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> Från: "Alan Franzoni" <mailing@franzoni.eu>
> Till: "Robin Rosenberg" <robin.rosenberg@dewire.com>
> Kopia: git@vger.kernel.org, "Alan Franzoni" <username@franzoni.eu>, schwab@linux-m68k.org
> Skickat: fredag, 27 jun 2014 10:24:23
> Ämne: Re: [PATCH] Fix: wrong offset for CET timezone
> 
> On Fri, Jun 27, 2014 at 12:08 AM, Robin Rosenberg
> <robin.rosenberg@dewire.com> wrote:
> > 1 hour in winter and 2 in summer, although some standards seem to say
> > that summer time is really called CEST, computers apply DST to CET in
> > summer.
> >
> > $ TZ=UTC date
> > Tor 26 Jun 2014 22:08:01 UTC
> >
> > $ TZ=CET date
> > Fre 27 Jun 2014 00:08:05 CEST
> 
> Like Andreas pointed out, this seems an implementation detail. CET is
> still +1, while CEST is +2.

I mentioned that myself...

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> If you take a look at the official IANA tzdata:
> 
> http://www.iana.org/time-zones/repository/releases/tzdata2014e.tar.gz
> 
> For europe, it's something like "std: CET" and "dst: CEST".
> 
> The current doc is not correct either; we should write something like
> "either +1 or +2 depending on DST" (there seems to be a 2dst as well
> which gets +3 offset);

I knew there gotta be a catch. I don't think glibc is advanced enough to provide two different summer times for the same TZ.

> Usually the best way of handling timezones is to use the proper
> location format (e.g. TZ='Europe/Rome') and then letting the system
> pick the proper offset; we might say something like ' "Europe/Rome"
> which is +1 in winter ' in the doc, but I'd say that's nitpicking.

Probably is. I think mentioning that CET can be either +1 or +2 is enough.

+ For example CET (here), which is nominally 1 hour ahead of UTC is encoded 
+ as `+0100`, but when summer savings apply, CET is two hours ahead and encoded
+ as `+0200`).

-- robin