com.jivesoftware.util
Class JulianDate

java.lang.Object
  |
  +--com.jivesoftware.util.JulianDate

public class JulianDate

extends Object

An implementation of a class used represent a Julian date. One very important thing to note about this class is that months ARE NOT zero based (unlike the Java Date class).

Author:

Matt Welsh (matt@matt-welsh.com)

Field Summary

protected double	et
protected GregorianCalendar	gregorianDate
protected double	jd
protected double	paramU

Constructor Summary

JulianDate()
Create a JD based on the current system time.

JulianDate(double jd)
Create a JD based on the given time.

JulianDate(int iYear, int month, int day)
Create a JD based on the given time.

JulianDate(int iYear, int month, int day, int hour, int min, int sec)
Create a JD based on the given time.

Method Summary

static GregorianCalendar	computeGregorianDate(double jDate) Compute a gregorian calendar date based on the given JD
static JulianDate	getCurrentJD()
double	getEphemerisTime() Returns the equivelent ephemeris time equivelent of this date.
GregorianCalendar	getGregorianDate() Returns the equivelent date on the Gregorian calendar.
double	getJulianCentury() Computes the number of Julian Centuries from 1900 Jan 0.5
double	getJulianDate() Gets the julian date as a double.
double	getParamU() Gets the "U" parameter used in high precision planetary computations.
String	toString() Return this object as a String.

Methods inherited from class java.lang.Object

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

Field Detail

jd

protected double jd

gregorianDate

protected GregorianCalendar gregorianDate

et

protected double et

paramU

protected double paramU

Constructor Detail

JulianDate

public JulianDate()

Create a JD based on the current system time.

JulianDate

public JulianDate(int iYear,
                  int month,
                  int day)

Create a JD based on the given time.

Parameters:

iYear - The year to use

month - The month to use (NOT ZERO BASED i.e. Jan = 1)

day - The day to use

JulianDate

public JulianDate(int iYear,
                  int month,
                  int day,
                  int hour,
                  int min,
                  int sec)

Create a JD based on the given time.

Parameters:

iYear - The year to use

month - The month to use (NOT ZERO BASED i.e. Jan = 1)

day - The day to use

hour - The hour to use

min - The minute to use

sec - The second to use

JulianDate

public JulianDate(double jd)

Create a JD based on the given time.

Parameters:

jd - The julian date as a double

Method Detail

getCurrentJD

public static JulianDate getCurrentJD()

getJulianDate

public double getJulianDate()

Gets the julian date as a double.

Returns:

The julian date as a double.

getJulianCentury

public double getJulianCentury()

Computes the number of Julian Centuries from 1900 Jan 0.5

Returns:

The number of Julian Centuries from 1900 Jan 0.5

getGregorianDate

public GregorianCalendar getGregorianDate()

Returns the equivelent date on the Gregorian calendar.

Returns:

the equivelent date on the Gregorian calendar.

getEphemerisTime

public double getEphemerisTime()

Returns the equivelent ephemeris time equivelent of this date. This is a more stable time scale than UT and is useful for high precision planetary computations.

Returns:

The ephemeris time representing this object.

getParamU

public double getParamU()

Gets the "U" parameter used in high precision planetary computations.

Returns:

The "U" parameter.

toString

public String toString()

Return this object as a String.

Overrides:

toString in class Object

Returns:

A String object representing this object.

computeGregorianDate

public static GregorianCalendar computeGregorianDate(double jDate)
                                              throws IllegalArgumentException

Compute a gregorian calendar date based on the given JD