@zodiacs/engine notice
========================

Astronomy Engine
----------------

The core runtime depends on astronomy-engine 2.1.19, Copyright (c) 2019-2023
Don Cross, distributed under the MIT License. Its distributed JavaScript source
retains the full MIT permission and warranty notice. Source and license metadata:
https://github.com/cosinekitty/astronomy

ΔT (TT − UT1)
------------

The package's ΔT module, the model "zodiacs-deltat/1" that the package
exports as @zodiacs/engine/deltat, contains 32 values of Table S15, rounded
to 0.01 s, and constants of equations (4.1) and (5.1) from the work below.
The build places that module in a shared chunk under dist/, which
dist/deltat.js re-exports, so the values are in that chunk rather than in
dist/deltat.js itself.

  Stephenson, F. R., Morrison, L. V. & Hohenkerk, C. Y. 2016, Measurement of
  the Earth's rotation: 720 BC to AD 2015. Proc. R. Soc. A 472: 20160404.
  doi:10.1098/rspa.2016.0404
  Published under Creative Commons Attribution 4.0 International (CC BY 4.0):
  https://creativecommons.org/licenses/by/4.0/
  The values are used unmodified except for rounding; the engine rebuilds the
  authors' spline from them.

Its values from 1941 come from the United States Naval Observatory
(historic_deltat.data and tai-utc.dat, US Government works) and from the
International Earth Rotation and Reference Systems Service (IERS EOP 20 C04
and Bulletin A, finals2000A.all), which asks that its products be cited:
IERS, https://www.iers.org/. They enter the table as 91 values in 0.01 s.

GeoNames
--------

The optional @zodiacs/engine/geo client can read a compact index derived from
GeoNames cities15000, admin1CodesASCII, and countryInfo. GeoNames data is
licensed under Creative Commons Attribution 4.0 International (CC BY 4.0):

  https://www.geonames.org/
  https://creativecommons.org/licenses/by/4.0/

The Zodiacs.org index rounds latitude and longitude to two decimal places,
interns timezone, administrative-area, and country strings, sorts cities by
population, and shards records by the first folded ASCII letter. No GeoNames
records are bundled in this npm package. If you host, copy, or redistribute a
compatible GeoNames-derived index, retain this notice and attribution.

Timezone data
-------------

@zodiacs/engine/geo does not redistribute the IANA Time Zone Database. Local
time conversion uses the host JavaScript runtime's Intl/ICU data. Historical
coverage, including pre-standardization local mean time, therefore depends on
the browser or Node.js build used by the consumer.
