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/*
* Copyright 2020 Adobe. All rights reserved.
* This file is licensed to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License. You may obtain a copy
* of the License at http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under
* the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
* OF ANY KIND, either express or implied. See the License for the specific language
* governing permissions and limitations under the License.
*/
// Portions of the code in this file are based on code from ICU.
// Original licensing can be found in the NOTICE file in the root directory of this source tree.
import {AnyCalendarDate, Calendar} from '../types';
import {CalendarDate} from '../CalendarDate';
import {mod, Mutable} from '../utils';
const EPOCH = 1721426; // 001/01/03 Julian C.E.
export function gregorianToJulianDay(era: string, year: number, month: number, day: number): number {
year = getExtendedYear(era, year);
let y1 = year - 1;
let monthOffset = -2;
if (month <= 2) {
monthOffset = 0;
} else if (isLeapYear(year)) {
monthOffset = -1;
}
return (
EPOCH -
1 +
365 * y1 +
Math.floor(y1 / 4) -
Math.floor(y1 / 100) +
Math.floor(y1 / 400) +
Math.floor((367 * month - 362) / 12 + monthOffset + day)
);
}
export function isLeapYear(year: number): boolean {
return year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0);
}
export function getExtendedYear(era: string, year: number): number {
return era === 'BC' ? 1 - year : year;
}
export function fromExtendedYear(year: number): [string, number] {
let era = 'AD';
if (year <= 0) {
era = 'BC';
year = 1 - year;
}
return [era, year];
}
const daysInMonth = {
standard: [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],
leapyear: [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
};
/**
* The Gregorian calendar is the most commonly used calendar system in the world. It supports two eras: BC, and AD.
* Years always contain 12 months, and 365 or 366 days depending on whether it is a leap year.
*/
export class GregorianCalendar implements Calendar {
identifier = 'gregory';
fromJulianDay(jd: number): CalendarDate {
let jd0 = jd;
let depoch = jd0 - EPOCH;
let quadricent = Math.floor(depoch / 146097);
let dqc = mod(depoch, 146097);
let cent = Math.floor(dqc / 36524);
let dcent = mod(dqc, 36524);
let quad = Math.floor(dcent / 1461);
let dquad = mod(dcent, 1461);
let yindex = Math.floor(dquad / 365);
let extendedYear = quadricent * 400 + cent * 100 + quad * 4 + yindex + (cent !== 4 && yindex !== 4 ? 1 : 0);
let [era, year] = fromExtendedYear(extendedYear);
let yearDay = jd0 - gregorianToJulianDay(era, year, 1, 1);
let leapAdj = 2;
if (jd0 < gregorianToJulianDay(era, year, 3, 1)) {
leapAdj = 0;
} else if (isLeapYear(year)) {
leapAdj = 1;
}
let month = Math.floor(((yearDay + leapAdj) * 12 + 373) / 367);
let day = jd0 - gregorianToJulianDay(era, year, month, 1) + 1;
return new CalendarDate(era, year, month, day);
}
toJulianDay(date: AnyCalendarDate): number {
return gregorianToJulianDay(date.era, date.year, date.month, date.day);
}
getDaysInMonth(date: AnyCalendarDate): number {
return daysInMonth[isLeapYear(date.year) ? 'leapyear' : 'standard'][date.month - 1];
}
// eslint-disable-next-line @typescript-eslint/no-unused-vars
getMonthsInYear(date: AnyCalendarDate): number {
return 12;
}
getDaysInYear(date: AnyCalendarDate): number {
return isLeapYear(date.year) ? 366 : 365;
}
// eslint-disable-next-line @typescript-eslint/no-unused-vars
getYearsInEra(date: AnyCalendarDate): number {
return 9999;
}
getEras() {
return ['BC', 'AD'];
}
isInverseEra(date: AnyCalendarDate): boolean {
return date.era === 'BC';
}
balanceDate(date: Mutable<AnyCalendarDate>) {
if (date.year <= 0) {
date.era = date.era === 'BC' ? 'AD' : 'BC';
date.year = 1 - date.year;
}
}
}
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