threads / patch / 37003

patchFix: wrong offset for CET timezone

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

## tl;dr

5 messages between Jun 26, 2014 and Jun 27, 2014. Diffs are folded; open one to read it.

replies: 4people: 3as markdown or json

Alan Franzoni· Jun 26, 2014, 13:53 UTC · lore

From: Alan Franzoni <username@franzoni.eu>

Signed-off-by: Alan Franzoni <username@franzoni.eu>
---
 Documentation/date-formats.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Show changes to Documentation/date-formats.txt +1 −1

diff --git a/Documentation/date-formats.txt b/Documentation/date-formats.txt
index ccd1fc8..284308a 100644
--- a/Documentation/date-formats.txt
+++ b/Documentation/date-formats.txt
@@ -11,7 +11,7 @@ Git internal format::
 	It is `<unix timestamp> <time zone offset>`, where `<unix
 	timestamp>` is the number of seconds since the UNIX epoch.
 	`<time zone offset>` is a positive or negative offset from UTC.
-	For example CET (which is 2 hours ahead UTC) is `+0200`.
+	For example CET (which is 1 hour ahead UTC) is `+0100`.
 
 RFC 2822::
 	The standard email format as described by RFC 2822, for example

-- 
2.0.0

Robin Rosenberg· Jun 26, 2014, 22:08 UTC · re: Alan Franzoni · lore

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

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

Show 23 quoted lines

> Från: "Alan Franzoni" <mailing@franzoni.eu>
> Till: git@vger.kernel.org
> Kopia: "Alan Franzoni" <username@franzoni.eu>
> Skickat: torsdag, 26 jun 2014 15:53:32
> Ämne: [PATCH] Fix: wrong offset for CET timezone
> 
> From: Alan Franzoni <username@franzoni.eu>
> 
> Signed-off-by: Alan Franzoni <username@franzoni.eu>
> ---
>  Documentation/date-formats.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/date-formats.txt b/Documentation/date-formats.txt
> index ccd1fc8..284308a 100644
> --- a/Documentation/date-formats.txt
> +++ b/Documentation/date-formats.txt
> @@ -11,7 +11,7 @@ Git internal format::
>  	It is `<unix timestamp> <time zone offset>`, where `<unix
>  	timestamp>` is the number of seconds since the UNIX epoch.
>  	`<time zone offset>` is a positive or negative offset from UTC.
> -	For example CET (which is 2 hours ahead UTC) is `+0200`.
> +	For example CET (which is 1 hour ahead UTC) is `+0100`.

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

-- robin

Show 10 quoted lines

>  RFC 2822::
>  	The standard email format as described by RFC 2822, for example
> --
> 2.0.0
> 
> --
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>

Andreas Schwab· Jun 27, 2014, 07:48 UTC · re: Robin Rosenberg · lore

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

Robin Rosenberg <robin.rosenberg@dewire.com> writes:

> $ TZ=CET date
> Fre 27 Jun 2014 00:08:05 CEST

That only works because CET is a special zone name (POSIX time zones require at least a number to denote the standard offset), similar to Europe/Berlin but without the history.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Alan Franzoni· Jun 27, 2014, 08:24 UTC · re: Robin Rosenberg · lore

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

On Fri, Jun 27, 2014 at 12:08 AM, Robin Rosenberg <robin.rosenberg@dewire.com> wrote:

Show 8 quoted lines

> 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.

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);

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.

-- 
contact me at public@[mysurname].eu

Robin Rosenberg· Jun 27, 2014, 08:51 UTC · re: Alan Franzoni · lore

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

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

Show 20 quoted lines

> 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...

Show 9 quoted lines

> 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