tads3/tz - This directory contains the files necessary to generate
the TADS 3 timezone database file, "timezones.t3tz", which should be
included with every source or binary distribution of TADS 3.

The timezone database is derived from the public domain IANA timezone
database source files, which can be found here:

   http://www.iana.org/time-zones

The timezone source files aren't included in the TADS distribution,
because the creators of those files would prefer to have a single
point of distribution to ensure quality control.

You don't actually need the IANA source files to build TADS, though.
The TADS source code distribution contains the pre-compiled database
file, "timezones.t3tz", which you can and should use directly.  This
will ensure that you're using the same version of the timezone
database that everyone else using this same version of TADS is using,
which will in turn ensure that you get date/time calculation results
that are consistent with everyone else's.

However, you *can* build your own new version of the compiled
timezones.t3tz file if you prefer.  The IANA database files are
revised from time to time, to correct errors, add new geographic
regions and historical data, and update zone definitions and daylight
savings rules to reflect the latest changes made by local authorities.
It's likely that the IANA files have been updated since the ones used
to create the latest TADS distribution.

If you do wish to update your TADS timezone database to the latest
IANA files without waiting for the official TADS distribution to catch
up, you can do so as follows.  But remember, if you do this, you might
see slightly different results in some cases from what other users
get for the same time/date calculations.

1. Download the latest IANA zoneinfo database files, and gunzip/untar
them into tads3/tz/db.

2. Compile and run the TADS timezone compiler, tads3/tz/tz.t:

    t3make -f tz.t3m
    t3run -plain tz.t3 db timezones.t3tz

3. Copy the generated file, timezones.t3tz, to your TADS executable
directory.
