Major parts of PDCLib's <time.h> implementation are based on IANA's reference
implementation, tzcode.

    https://data.iana.org/time-zones/tz-link.html

The latest version of tzcode can be downloaded at:

    https://www.iana.org/time-zones/repository/tzcode-latest.tar.gz

At the time of this writing, the latest tzcode version used as basis is 2020a.