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Help me understand time zones

Dave Rolsky
January 24, 2003 15:57
Help me understand time zones
Message ID:
So I'm hacking away at time zone code and getting darn close to producing
something usable, dare I even say elegant?  We'll see on both counts, I
suppose ;)

Anyway, I've been working with the raw Olson DB the last couple days, and
I've produced a parser that can read its "rules", "zones", "links" and
turn them into useful data structures, generate sequences of "changes"
(when a particular zone changes something like its short name (CST =>
CWT), or a DST change (offset changes) or its offset (LMT times to modern

But now I have an important question.  The time zones defined in the Olson
DB are not complete, merely representative.

For example, I live in Minneapolis, Minnesota, US.  The time zone
definitions nearest to me are "America/Chicago", "America/Menominee" (a
small town in Wisconsin).  Minnesota is "represented" by Chicago.

The America/Chicago zone has a number of different observances, and during
some of them it applies the "US" rules", while during others it applies
the "Chicago" rules.

My question is are the Chicago rules broadly applicable to all places
using US Central time?  Obviously, a few are specified differently
(Menominee), but most seem to just be lumped in with Chicago.

I'm assuming, from reading the comments in the file, that this is indeed
correct, but I'd greatly appreciate some confirmation on this point.


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