[Kde-pim] vzic (Was:libical 0.27 is now available)

[Allen Winter]

On Monday 26 March 2007 7:00:39 am Reinhold Kainhofer wrote:
> Am Montag, 26. März 2007 schrieb David Jarvie:
> > On Sat, March 24, 2007 2:56 pm, Allen Winter wrote:
> > > On Wednesday 21 March 2007 6:06:51 pm Reinhold Kainhofer wrote:
> > >> Am Mittwoch, 28. Februar 2007 schrieb IGnatius T Foobar:
> > >> >  For anyone interested...
> > >> >
> > >> >    http://easyinstall.citadel.org/libical-0.27.tar.gz
> > >> >
> > >> >  tzdata is updated to 2007c (includes the changes for Daylight Savings
> > >> > Time in the US) as well as a couple of minor bugfixes.
> > >>
> > >> I took a look at the files now, and it seems that the DST changes in the
> > >> US
> > >> were implemented wrong. The files contain e.g.
> > >
> > > We need to have a fix right away.
> > > What to do?
> > > http://bugs.kde.org/show_bug.cgi?id=143409
> >
> > This has jogged my memory about a bug I discovered some time ago in the
> > libical time zone definitions. They were updated about a year ago by
> > Tepper Hasso. Many of the definitions are actually completely wrong in the
> > same manner as the new USA definitions. For example, Europe/London also
> > has only a single blanket definition starting in 1970, whereas the
> > previous (correct) version has many different definitions for different
> > years starting in the 19th century. The current version is wrong even for
> > some years post-1970. Tepper's commit needs to be reverted, and then the
> > new USA stuff needs to be added.
> 
> Actually, the Olsen database is a comprehensive database of all historical DST
> occurrences, too. So basically all that we need is a proper converter from
> the ODB to iCalendar... There are such converters, but I don't know how good
> they work.
> See http://www.twinsun.com/tz/tz-link.htm
> 
> Only using the system-wide zoneinfo files, it will never be possible to
> properly generate historical times.
> 
> I don't have time currently to look into that issue with really broken TZ
> definitions... I suppose unless we find an easy cleaner solution, it is best
> now to use the wrong fix and in the future generate proper VTIMEZONE
> snipplets with all historical data directly from the Olsen DB.
> 

I found the vzic program as mentioned in the above URL.
I run vzic with the --pure option which is documented
to generate "exact data"  from the Olson database.

The generated America/New_York.ics is attached .
Please review and let me know if it looks ok.

Interestingly, the default behavior of vzic is to write
the .ics files to be compatible with Outlook 2000.
When I run it in default mode the resulting .ics
files are identical to that found in libical-0.27.

If this works, we can now generate the zoneinfo .ics
files ourselves from the official Olson database tzdata.

Regards,
Allen
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