[tz] time zones only ?

Tim Parenti tim at timtimeonline.com
Thu Feb 25 23:50:51 UTC 2021

On Thu, 25 Feb 2021 at 18:20, William Karlsson via tz <tz at iana.org> wrote:

> Is there a simple way to compile only the timezones ? i.e. US/Central
> etc... No cities ?

In short, no.  Most of the identifiers of that type are merely backwards
compatibility links to other zones named in the conventional way, like
America/Chicago, and so can't really be compiled alone.  See the 'backward'

Slightly longer, the notion of a "time zone" as you describe is ("Eastern",
"Central", etc.) is actually quite ill-defined.  While in the US, we are
accustomed to a certain level of legislated uniformity in our timekeeping,
in other parts of the world, clocks in various countries and regions often
agree (or disagree) with their neighbors' out of coincidence arising from
mutual convenience.  For example, there is not really such a thing as
"Central African Time" as a standard that is to be followed; rather, there
just happen to be countries and regions that, for their various reasons,
choose to observe UTC+2, and "Central African Time" is a name that some
have used to describe that common trait to facilitate communication.

Even within the US, where your concept of "time zones" is a bit better
defined: Clocks in Phoenix match Denver in the winter time, but match Los
Angeles in the summer.  Is that best described as "Mountain"?  Or
"Pacific"?  Is it both, neither, or something altogether different?
Depending on the precise questions you're asking, that can get complicated
quickly, before questions of how historical timekeeping practices diverged
in neighboring regions even come up.

These are the main factors contributing to the approach our database takes
instead: Provide a representative location for each region where clocks
have agreed since an arbitrary cutoff (in our case, 1970).  In particular,
there are generally many such regions ("time zones" in our technical sense)
within what we might think of as a "time zone" in a more cultural sense.
For more detail, see the "Scope of the tz database" and "Timezone
identifiers" sections of 'theory.html'.

* * *

On the other hand, if you're really just looking for the
nautical/navigational "zones" that form 15-degree-wide bands from pole to
pole and don't account for geopolitical boundaries or any civil quirks like
Daylight Saving Time, the 'etcetera' file has those; however, their limited
utility makes them ill-suited for most real-world applications, and again,
they are only really present for backwards compatibility.  (Most
confusingly the +/- signs in those names are the opposite of the
now-standard conventions.)  I would advise against their use in anything

We may be able to point you in a better direction if you'd tell us more
about what you're specifically trying to accomplish.

Tim Parenti

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