org.josef.util

Class JulianDate

java.lang.Object

org.josef.util.JulianDate

@Status(stage=PRODUCTION,
        unitTests=COMPLETE)
 @Review(by="Kees Schotanus",
        at="2009-09-28")
public final class JulianDate
extends Object

Utility class to calculate Julian Dates.
To be precise, this class currently only supports Julian days which can be presented as an integer, the time part which requires floats is left out
A Julian day is the absolute count of days since January first 4712BC. 4712BC is supposed to be a day before which no historical events were known. It is also a date for which other cyclic calendars based upon the sun, moon or Roman indiction had an ordinal of 1. Julian days are an invention of "Joseph Scaliger" who lived from 1540 to 1609. Several web pages exist that clarify Julian Dates. You can check out: this page for another explanation.

Version:

1.0 $Revision: 3936 $

Author:

Kees Schotanus

Method Summary

Modifier and Type	Method and Description
static GregorianCalendar	getDate(int julianDay) Converts the supplied Julian day to a Gregorian year, month and day.
static int	getJulianDay(int year, int month, int day) Computes the Julian day from the supplied year, month and day.
static int	getJulianDay(long milliseconds) /** Converts the supplied time in milliseconds since the EPOCH to a Julian date.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getJulianDay

public static int getJulianDay(int year,
                               int month,
                               int day)

Computes the Julian day from the supplied year, month and day.

Parameters:

year - Gregorian year.
-4712 <= year <= 9999. To be safe it is best to use a date after the year 1800.

month - Ordinal month number. 1 <= month <= 12

day - Ordinal day number. 1 <= day <= maximumDayForSuppliedMonth

Returns:

Julian day number.

Throws:

IllegalArgumentException - When one of the input parameters is out of range.

getJulianDay

public static int getJulianDay(long milliseconds)

/** Converts the supplied time in milliseconds since the EPOCH to a Julian date.
The EPOCH is the birth date of Unix and is equal to January first, 1970 according to the Gregorian calendar.

Parameters:

milliseconds - Time in milliseconds since the EPOCH.
May be negative for time before the EPOCH.

Returns:

Julian day.

getDate

public static GregorianCalendar getDate(int julianDay)

Converts the supplied Julian day to a Gregorian year, month and day.

Parameters:

julianDay - The Julian day to convert. The Julian day should not be a day before March 1 in the year 0.

Returns:

An array where the first element contains the year, the second element contains the month and the third and final element contains the day.

Throws:

IllegalArgumentException - When the input Julian day represents a day before Christ was born.