Module: seasons

Dates of tropical events for a given Milesian year. These functions implement Jean Meeus' method for computing tropical events. The code derives from Fourmilab's astro.js file (2015). Code has been modified in order to conform with strict mode.
Version:
  • M2021-08-20
Author:
  • Louis A. de Fouquières https://github.com/Louis-Aime
License:
  • MIT 2016-2022
Source:

Requires

  • module:getdeltat

Methods

(static) equinox(year, which) → {number}

The Julian Day of a tropical event (equinox or solstice) of a given year. This function implements Jean Meeus' method for calculating equinox and solstices dates of a given year. This implementation is extracted from Fourmilab's astro functions (John Walker, http://www.fourmilab.ch/, September MIM).
Parameters:
Name Type Description
year number the Gregorian year.
which number 0->March, 1->June, 2->September, 3->December, any other value -> Error.
Source:
Returns:
the date of the event in Julian Day, Terrestrial Time.
Type
number

(static) tropicEvent(year, which) → {Date}

Compute a tropical event of a Milesian year, result as a Date. Milesian year means the year beginning at a northern winter solstice and finishing at the next northern winter solstice.
Parameters:
Name Type Description
year number the Milesian year
which number the season, coded as: 0->Winter solstice at beginning of year, 1->Spring equinox, 2->Summer solstice, 3->Autumn equinox, 4->Winter solstice at end of year, any other value -> Error.
Source:
Returns:
the date of the event (correction with an estimate of Delta T).
Type
Date