64 lines
1.5 KiB
JavaScript
64 lines
1.5 KiB
JavaScript
'use strict';
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var astronomia = require('astronomia');
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var Chinese = require('./Chinese.cjs');
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/**
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* @copyright 2016 commenthol
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* @license MIT
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*/
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// Start of Korean Calendar in 2333 BCE (단군기원 http://ko.wikipedia.org/wiki/단기)
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const epochY = -2333;
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const epoch = new astronomia.julian.CalendarGregorian(epochY, 1, 27).toJDE();
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/**
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* change of timezone shifts during the last century
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* @see https://en.wikipedia.org/wiki/Time_in_South_Korea
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*/
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const UTC_DATES = [
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{
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date: new Date('1961-10-09T15:00:00.000Z'), // 1961-10-10T00:00:00+0900
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shift: 9 / 24
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}, // +9:00:00h (135° East)
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{
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date: new Date('1954-03-20T15:30:00.000Z'), // 1954-03-21T00:00:00+0830
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shift: 8.5 / 24
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},
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{
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date: new Date('1911-12-31T15:00:00.000Z'), // 1912-01-01T00:00:00+0900
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shift: 9 / 24
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},
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{
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date: new Date('1908-03-31T15:30:00.000Z'), // 1908-04-01T00:00:00+0830
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shift: 8.5 / 24
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}
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];
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class CalendarKorean extends Chinese {
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constructor (cycle, year, month, leap, day) {
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super(cycle, year, month, leap, day);
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this._epochY = epochY;
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this._epoch = epoch;
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}
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/**
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* timeshift to UTC
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*
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* @param {CalendarGregorian} gcal - gregorian calendar date
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* @return {Number} timeshift in fraction of day
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*/
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timeshiftUTC (gcal) {
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const date = gcal.toDate();
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for (const i in UTC_DATES) {
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if (date >= UTC_DATES[i].date) {
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return UTC_DATES[i].shift
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}
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}
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return 3809 / 450 / 24 // +8:27:52h Seoul City Hall 126°58'E
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}
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}
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module.exports = CalendarKorean;
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