[tz] Getting current tzdb version in use

[Robert Elz]

    Date:        Fri, 20 Jul 2018 10:12:22 -0400
    From:        Paul G <paul at ganssle.io>
    Message-ID:  <76b9ed1b-b097-f483-2709-dddf02ad0e37 at ganssle.io>

  | You guys know this thread was not sent to the main list? 

I just did a random check on mesages in my copies, and they all
look to have been sent to tz at iana.org - what makes you think
otherwise?  And what other list is there they could have been sent to?

  | I can tell you a few places I've found need for the version:
  |
  | 1. I have some tests in my test suite that check certain edge cases, one =
  | of which is the international date line switch in Kiribati in 1994.

The right way to test that is to check the translation of 1994-12-31
in the Kiribati timezone, and see what UTC value you get.   That way,
regardless of who fixed what, or when, or in what random patch to
what version, you'll always find out what you should use.   To be even more
flexible you could work through some times, in case some other random
version had the transition listed at yet another point in time.


  | 2. It is useful to check the version to see if the system version is outdated

This is a package manager issue - and yes, software installers need to
keep track of which versions are installed, or everything...

  | 3. It can be useful when you have the choice of more than one source for
  | time zone data

Same thing.

  | In all of these cases, I believe that *some* version information would be
  | better than none, even if not all the complexity of what it means to be
  | a "new version" is captured.

We have that now, and ave for some time (and on NetBSD, before the
version file appeared in txdata, we had a TZDATA_VERSION which
served the same purpose ... we still do...)

  | At this point, of course, I think the battle in the tz project is won - tzdata.zi
  | exists and last I checked `make install` installs it into `/usr/share/zoneinfo`,
  | so now it's time to get system distributors to make sure they include it in
  | their distributions, I guess.

Which we don't in NetBSD, that file adds no value for us.

kre