Astronomy Engine 2.1.19 by Don Cross — MIT license (see astronomy-LICENSE.txt).
Source: https://github.com/cosinekitty/astronomy/tree/v2.1.19

City catalogue derived from GeoNames cities500, downloaded 2026-09-02.
Source: https://download.geonames.org/export/dump/cities500.zip
License: Creative Commons Attribution 4.0, https://creativecommons.org/licenses/by/4.0/
Changes: selected name, country, administrative region name, coordinates, IANA zone,
ASCII name; sorted by population; converted TSV to JSON with admin1CodesASCII region labels. 235,640 entries, split by country.
GeoNames data is provided without warranty. https://www.geonames.org/

Historical timezone rules: PHP's installed IANA timezone database.