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With inspiration from other libraries
// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/**
*******************************************************************************
* Copyright (C) 2003-2014, International Business Machines Corporation and
* others. All Rights Reserved.
*******************************************************************************
* Partial port from ICU4C's Grego class in i18n/gregoimp.h.
*
* Methods ported, or moved here from OlsonTimeZone, initially
* for work on Jitterbug 5470:
* tzdata2006n Brazil incorrect fall-back date 2009-mar-01
* Only the methods necessary for that work are provided - this is not a full
* port of ICU4C's Grego class (yet).
*
* These utilities are used by both OlsonTimeZone and SimpleTimeZone.
*/
package com.ibm.icu.impl;
import java.util.Locale;
/**
* A utility class providing proleptic Gregorian calendar functions
* used by time zone and calendar code. Do not instantiate.
*
* Note: Unlike GregorianCalendar, all computations performed by this
* class occur in the pure proleptic GregorianCalendar.
*/
public class Grego {
// Max/min milliseconds
public static final long MIN_MILLIS = -184303902528000000L;
public static final long MAX_MILLIS = 183882168921600000L;
public static final int MILLIS_PER_SECOND = 1000;
public static final int MILLIS_PER_MINUTE = 60*MILLIS_PER_SECOND;
public static final int MILLIS_PER_HOUR = 60*MILLIS_PER_MINUTE;
public static final int MILLIS_PER_DAY = 24*MILLIS_PER_HOUR;
// January 1, 1 CE Gregorian
private static final int JULIAN_1_CE = 1721426;
// January 1, 1970 CE Gregorian
private static final int JULIAN_1970_CE = 2440588;
private static final int[] MONTH_LENGTH = new int[] {
31,28,31,30,31,30,31,31,30,31,30,31,
31,29,31,30,31,30,31,31,30,31,30,31
};
private static final int[] DAYS_BEFORE = new int[] {
0,31,59,90,120,151,181,212,243,273,304,334,
0,31,60,91,121,152,182,213,244,274,305,335 };
/**
* Return true if the given year is a leap year.
* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
* @return true if the year is a leap year
*/
public static final boolean isLeapYear(int year) {
// year&0x3 == year%4
return ((year&0x3) == 0) && ((year%100 != 0) || (year%400 == 0));
}
/**
* Return the number of days in the given month.
* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
* @param month 0-based month, with 0==Jan
* @return the number of days in the given month
*/
public static final int monthLength(int year, int month) {
return MONTH_LENGTH[month + (isLeapYear(year) ? 12 : 0)];
}
/**
* Return the length of a previous month of the Gregorian calendar.
* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
* @param month 0-based month, with 0==Jan
* @return the number of days in the month previous to the given month
*/
public static final int previousMonthLength(int year, int month) {
return (month > 0) ? monthLength(year, month-1) : 31;
}
/**
* Convert a year, month, and day-of-month, given in the proleptic
* Gregorian calendar, to 1970 epoch days.
* @param year Gregorian year, with 0 == 1 BCE, -1 == 2 BCE, etc.
* @param month 0-based month, with 0==Jan
* @param dom 1-based day of month
* @return the day number, with day 0 == Jan 1 1970
*/
public static long fieldsToDay(int year, int month, int dom) {
int y = year - 1;
long julian =
365 * y + floorDivide(y, 4) + (JULIAN_1_CE - 3) + // Julian cal
floorDivide(y, 400) - floorDivide(y, 100) + 2 + // => Gregorian cal
DAYS_BEFORE[month + (isLeapYear(year) ? 12 : 0)] + dom; // => month/dom
return julian - JULIAN_1970_CE; // JD => epoch day
}
/**
* Return the day of week on the 1970-epoch day
* @param day the 1970-epoch day (integral value)
* @return the day of week
*/
public static int dayOfWeek(long day) {
long[] remainder = new long[1];
floorDivide(day + 5 /* Calendar.THURSDAY */, 7, remainder);
int dayOfWeek = (int)remainder[0];
dayOfWeek = (dayOfWeek == 0) ? 7 : dayOfWeek;
return dayOfWeek;
}
public static int[] dayToFields(long day, int[] fields) {
if (fields == null || fields.length < 5) {
fields = new int[5];
}
// Convert from 1970 CE epoch to 1 CE epoch (Gregorian calendar)
day += JULIAN_1970_CE - JULIAN_1_CE;
long[] rem = new long[1];
long n400 = floorDivide(day, 146097, rem);
long n100 = floorDivide(rem[0], 36524, rem);
long n4 = floorDivide(rem[0], 1461, rem);
long n1 = floorDivide(rem[0], 365, rem);
int year = (int)(400 * n400 + 100 * n100 + 4 * n4 + n1);
int dayOfYear = (int)rem[0];
if (n100 == 4 || n1 == 4) {
dayOfYear = 365; // Dec 31 at end of 4- or 400-yr cycle
}
else {
++year;
}
boolean isLeap = isLeapYear(year);
int correction = 0;
int march1 = isLeap ? 60 : 59; // zero-based DOY for March 1
if (dayOfYear >= march1) {
correction = isLeap ? 1 : 2;
}
int month = (12 * (dayOfYear + correction) + 6) / 367; // zero-based month
int dayOfMonth = dayOfYear - DAYS_BEFORE[isLeap ? month + 12 : month] + 1; // one-based DOM
int dayOfWeek = (int)((day + 2) % 7); // day 0 is Monday(2)
if (dayOfWeek < 1 /* Sunday */) {
dayOfWeek += 7;
}
dayOfYear++; // 1-based day of year
fields[0] = year;
fields[1] = month;
fields[2] = dayOfMonth;
fields[3] = dayOfWeek;
fields[4] = dayOfYear;
return fields;
}
/*
* Convert long time to date/time fields
*
* result[0] : year
* result[1] : month
* result[2] : dayOfMonth
* result[3] : dayOfWeek
* result[4] : dayOfYear
* result[5] : millisecond in day
*/
public static int[] timeToFields(long time, int[] fields) {
if (fields == null || fields.length < 6) {
fields = new int[6];
}
long[] remainder = new long[1];
long day = floorDivide(time, 24*60*60*1000 /* milliseconds per day */, remainder);
dayToFields(day, fields);
fields[5] = (int)remainder[0];
return fields;
}
public static long floorDivide(long numerator, long denominator) {
// We do this computation in order to handle
// a numerator of Long.MIN_VALUE correctly
return (numerator >= 0) ?
numerator / denominator :
((numerator + 1) / denominator) - 1;
}
private static long floorDivide(long numerator, long denominator, long[] remainder) {
if (numerator >= 0) {
remainder[0] = numerator % denominator;
return numerator / denominator;
}
long quotient = ((numerator + 1) / denominator) - 1;
remainder[0] = numerator - (quotient * denominator);
return quotient;
}
/*
* Returns the ordinal number for the specified day of week in the month.
* The valid return value is 1, 2, 3, 4 or -1.
*/
public static int getDayOfWeekInMonth(int year, int month, int dayOfMonth) {
int weekInMonth = (dayOfMonth + 6)/7;
if (weekInMonth == 4) {
if (dayOfMonth + 7 > monthLength(year, month)) {
weekInMonth = -1;
}
} else if (weekInMonth == 5) {
weekInMonth = -1;
}
return weekInMonth;
}
/**
* Convenient method for formatting time to ISO 8601 style
* date string.
* @param time long time
* @return ISO-8601 date string
*/
public static String timeToString(long time) {
int[] fields = timeToFields(time, null);
int millis = fields[5];
int hour = millis / MILLIS_PER_HOUR;
millis = millis % MILLIS_PER_HOUR;
int min = millis / MILLIS_PER_MINUTE;
millis = millis % MILLIS_PER_MINUTE;
int sec = millis / MILLIS_PER_SECOND;
millis = millis % MILLIS_PER_SECOND;
return String.format((Locale)null, "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ",
fields[0], fields[1] + 1, fields[2], hour, min, sec, millis);
}
}