21.1: calendar: daylight saving time wrong

21.1: calendar: daylight saving time wrong

[Ulrich Windl]

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In GNU Emacs 21.1.1 (i386-msvc-nt4.0.1381)
 of 2001-10-22 on buffy
configured using `configure --with-msvc (12.00)'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: DEU
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

In Emacs 21.1 the begin of DST in Europe is maked for April 7th in
calendar, while it actually happens on March, 31. In Emacs 20.7 (on Linux)
it seems correct however.


Recent input:
M-x c a l e n d a r <return> <help-echo> <help-echo> 
<down-mouse-1> <mouse-1> <help-echo> S <help-echo> 
h <help-echo> h <down> <down> <down> <up> <up> <up> 
<down> <down> <down> <down> <up> <up> <up> <up> <up> 
<up> <down> h <help-echo> <help-echo> <help-echo> <help-echo> 
M-x r e p <tab> o <tab> r <tab> <return>

Recent messages:
Marking holidays...done
Marking diary entries...done
Marking holidays...done
Marking diary entries...done
Checking holidays...
Sunday, 31 March 2002:  Easter Sunday
Making completion list...
Loading view...done
Making completion list...
Loading emacsbug...done


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Re: 21.1: calendar: daylight saving time wrong

[Jason Rumney]

"Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:

> In Emacs 21.1 the begin of DST in Europe is maked for April 7th in
> calendar, while it actually happens on March, 31. In Emacs 20.7 (on Linux)
> it seems correct however.

This is most likely a bug in the underlying system libraries.  MSVC is
notorious for poor handling of timezones, especially in the southern
hemisphere.


-- 
Jason Rumney

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Re: 21.1: calendar: daylight saving time wrong

[Ulrich Windl]

On 22 Mar 2002, at 9:09, Ed Reingold wrote:

> > In Emacs 21.1 the begin of DST in Europe is maked for April 7th in
> > calendar, while it actually happens on March, 31. In Emacs 20.7 (on Linux)
> > it seems correct however.
> 
> The DST information comes from the operating system, not from within Emacs.

Yes, however "TZEDIT from the Windows Resource kit says DST switching 
will take effect on last sunday in March. Now I wonder whether either 
the emacs code gets it wrong from the OS, or Windows/NT 4.0 has no idea 
what the last sunday in march is. Note that the last sunday in march is 
the last day in march this year (31st). Maybe Microsoft messed it up...

Ulrich

Re: 21.1: calendar: daylight saving time wrong

[Ralf Fassel]

* "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de>
| Note that the last sunday in march is the last day in march this
| year (31st). Maybe Microsoft messed it up...

Might be related to the counting of weeks and whether a week starts at
sunday or monday.  IRIX 5 also has this problem, where IRIX 6 has not
with the same setting of TZ.

R'

Re: 21.1: calendar: daylight saving time wrong

[Jason Rumney]

"Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de> writes:

> > The DST information comes from the operating system, not from within Emacs.
> 
> Yes, however "TZEDIT from the Windows Resource kit says DST switching 
> will take effect on last sunday in March.

From my previous correspondence with Microsoft about bugs in their
C library implementation of timezones, I can tell you that what TZEDIT
tells about NT's knowledge of timezones may have no bearing on what
the C library does.  The implementation of timezones in the OS itself,
and in Microsoft's proprietary API for accessing this info seems to be
bug free, it is their C library that is buggy.

-- 
Jason Rumney