/tads3/tz/db/
This directory is in the TADS 3 source code distribution as a placeholder for the IANA timezone database file. They're not included in the TADS distribution, but these public domain files are available from the IANA site at
Download the zoneinfo database files and gunzip/untar them into this directory.
You can then run the TADS timezone compiler, tz.t, which should be in this directory's parent folder.
Run these commands in that parent folder to build the compiler and compile the database:
t3make -f tz.t3m
t3run -plain tz db vmtz.cpp
The t3run tz command will read the timezone database files from the db folder and generate the output file vmtz.cpp.
That file can then be copied into the TADS source tree in the tads3/derived folder to replace the previous generated version.