DST start/end comments

Oscar van Vlijmen o.van.vlijmen at tip.nl
Mon Jan 31 22:26:22 UTC 2000


Thanks for your email with several comments on, well, let's say the art of
being up to date.

My DST start/end list has been compiled from the tzdata2000a data, with the
aid of a Macintosh HyperCard application I developed recently.

I intend to follow the _published tzdata_ closely, even if somebody on the
tz-mailing list tells that there could be something wrong. As fas as I can
guess, it is up to Paul Eggert to make decisions about all new information
and proposals and up to Arthur Olson to produce new tzcode and tzdata
files. This process takes a while.
The Australia data is in study and confirmation has been asked; cf. Paul's
email to Margaret Turner, Jan. 22.

I am following time zone information on the Internet for several years and
I have found that the tzdata information seems to be the most up to date
and the most accurate. Probably not 100% accurate, but consistently the
most up to date and the most accurate.
There are many web pages in existence which use the tzdata information
themselves, but I have found that in many cases they do not use the latest
I looked today at timezoneconverter.com and I had the impression that they
are using the tzdata1999h information from October 1999

The site of Steffen Thorsen (http://www.timeanddate.com) deserves to be
listed on the tz-link.htm page.
On his credits page he writes:
"These are resources available on the net, which has helped very much
during the development and maintenance of
this site.
The Time Zone Database - maintained by Arthur David Olson, Paul Eggert and
hundreds of volunteers,
available at ftp://elsie.nci.nih.gov/pub/ - much of time zone information
is obtained here".
I particularly like his neat webinterface and many functions. He seems to
be pretty up to date, but it looks like he uses predominantly tzdata, so
probably nothing new here.

About the time formats used in tzdata files.
I agree with you that it looks a bit like a mess, but the format is clearly
explained in the file zic.8 in the tzcode folder.
A time followed by w is 'wall clock' time, followed by s is local standard
time, followed by u, g or z is universal time. Without a subsequent letter
wall clock time is assumed.
My interpretations: 'wall clock' time is the current local time, which
could be wintertime or summertime. The 'local standard' time is always the
local wintertime. 'Universal' time is the same as UTC.

Although this is a reaction to a more or less private email, I hope you
don't mind if I send my email in copy to the tz-mailing list, since it is
possible that the answers are useful to more people. Even then, some of my
interpretations could be wrong and I would like to be corrected on them.


Oscar van Vlijmen

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