java.lang.Object
- com.ibm.icu.impl.CalendarAstronomer

```
public class CalendarAstronomer
extends Object
```
CalendarAstronomer is a class that can perform the calculations to determine the positions of the sun and moon, the time of sunrise and sunset, and other astronomy-related data. The calculations it performs are in some cases quite complicated, and this utility class saves you the trouble of worrying about them.
The measurement of time is a very important part of astronomy. Because astronomical bodies are constantly in motion, observations are only valid at a given moment in time. Accordingly, each CalendarAstronomer object has a time property that determines the date and time for which its calculations are performed. You can set and retrieve this property with setDate, getDate and related methods.
Almost all of the calculations performed by this class, or by any astronomer, are approximations to various degrees of accuracy. The calculations in this class are mostly modelled after those described in the book Practical Astronomy With Your Calculator, by Peter J. Duffett-Smith, Cambridge University Press, 1990. This is an excellent book, and if you want a greater understanding of how these calculations are performed it a very good, readable starting point.
WARNING: This class is very early in its development, and it is highly likely that its API will change to some degree in the future. At the moment, it basically does just enough to support IslamicCalendar and ChineseCalendar.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`CalendarAstronomer.Ecliptic`	Represents the position of an object in the sky relative to the ecliptic, the plane of the earth's orbit around the Sun.
`static class`	`CalendarAstronomer.Equatorial`	Represents the position of an object in the sky relative to the plane of the earth's equator.
`static class`	`CalendarAstronomer.Horizon`	Represents the position of an object in the sky relative to the local horizon.

Field Summary

Fields
Modifier and Type	Field	Description
`static com.ibm.icu.impl.CalendarAstronomer.SolarLongitude`	`AUTUMN_EQUINOX`	Constant representing the autumnal equinox.
`static long`	`DAY_MS`	The number of milliseconds in one day.
`static com.ibm.icu.impl.CalendarAstronomer.MoonAge`	`FIRST_QUARTER`	Constant representing the moon's first quarter.
`static com.ibm.icu.impl.CalendarAstronomer.MoonAge`	`FULL_MOON`	Constant representing a full moon.
`static int`	`HOUR_MS`	The number of milliseconds in one hour.
`static long`	`JULIAN_EPOCH_MS`	The start of the julian day numbering scheme used by astronomers, which is 1/1/4713 BC (Julian), 12:00 GMT.
`static com.ibm.icu.impl.CalendarAstronomer.MoonAge`	`LAST_QUARTER`	Constant representing the moon's last quarter.
`static int`	`MINUTE_MS`	The number of milliseconds in one minute.
`static com.ibm.icu.impl.CalendarAstronomer.MoonAge`	`NEW_MOON`	Constant representing a new moon.
`static int`	`SECOND_MS`	The number of milliseconds in one second.
`static double`	`SIDEREAL_DAY`	The number of standard hours in one sidereal day.
`static double`	`SIDEREAL_MONTH`	The average number of days it takes for the moon to return to the same ecliptic longitude relative to the stellar background.
`static double`	`SIDEREAL_YEAR`	The average number of days it takes for the sun to return to the same position against the fixed stellar background.
`static double`	`SOLAR_DAY`	The number of sidereal hours in one mean solar day.
`static com.ibm.icu.impl.CalendarAstronomer.SolarLongitude`	`SUMMER_SOLSTICE`	Constant representing the summer solstice.
`static double`	`SYNODIC_MONTH`	The average number of solar days from one new moon to the next.
`static double`	`TROPICAL_YEAR`	The average number number of days between successive vernal equinoxes.
`static com.ibm.icu.impl.CalendarAstronomer.SolarLongitude`	`VERNAL_EQUINOX`	Constant representing the vernal equinox.
`static com.ibm.icu.impl.CalendarAstronomer.SolarLongitude`	`WINTER_SOLSTICE`	Constant representing the winter solstice.

Constructor Summary

Constructors
Constructor	Description
`CalendarAstronomer()`	Construct a new `CalendarAstronomer` object that is initialized to the current date and time.
`CalendarAstronomer(double longitude, double latitude)`	Construct a new `CalendarAstronomer` object with the given latitude and longitude.
`CalendarAstronomer(long aTime)`	Construct a new `CalendarAstronomer` object that is initialized to the specified time.
`CalendarAstronomer(Date d)`	Construct a new `CalendarAstronomer` object that is initialized to the specified date and time.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`CalendarAstronomer.Equatorial`	`eclipticToEquatorial(double eclipLong)`	Convert from ecliptic longitude to equatorial coordinates.
`CalendarAstronomer.Equatorial`	`eclipticToEquatorial(double eclipLong, double eclipLat)`	Convert from ecliptic to equatorial coordinates.
`CalendarAstronomer.Equatorial`	`eclipticToEquatorial(CalendarAstronomer.Ecliptic ecliptic)`	Convert from ecliptic to equatorial coordinates.
`CalendarAstronomer.Horizon`	`eclipticToHorizon(double eclipLong)`
`Date`	`getDate()`	Get the current time of this `CalendarAstronomer` object, represented as a `Date` object.
`double`	`getGreenwichSidereal()`	Returns the current Greenwich sidereal time, measured in hours
`double`	`getJulianCentury()`	Return this object's time expressed in julian centuries: the number of centuries after 1/1/1900 AD, 12:00 GMT
`double`	`getJulianDay()`	Get the current time of this `CalendarAstronomer` object, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT.
`double`	`getLocalSidereal()`	Returns the current local sidereal time, measured in hours
`double`	`getMoonAge()`	The "age" of the moon at the time specified in this object.
`double`	`getMoonPhase()`	Calculate the phase of the moon at the time set in this object.
`CalendarAstronomer.Equatorial`	`getMoonPosition()`	The position of the moon at the time set on this object, in equatorial coordinates.
`long`	`getMoonRiseSet(boolean rise)`	Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.
`long`	`getMoonTime(double desired, boolean next)`	Find the next or previous time at which the Moon's ecliptic longitude will have the desired value.
`long`	`getMoonTime(com.ibm.icu.impl.CalendarAstronomer.MoonAge desired, boolean next)`	Find the next or previous time at which the moon will be in the desired phase.
`double`	`getSunLongitude()`	The longitude of the sun at the time specified by this object.
`CalendarAstronomer.Equatorial`	`getSunPosition()`	The position of the sun at this object's current date and time, in equatorial coordinates.
`long`	`getSunRiseSet(boolean rise)`	Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.
`long`	`getSunTime(double desired, boolean next)`	Find the next time at which the sun's ecliptic longitude will have the desired value.
`long`	`getSunTime(com.ibm.icu.impl.CalendarAstronomer.SolarLongitude desired, boolean next)`	Find the next time at which the sun's ecliptic longitude will have the desired value.
`long`	`getTime()`	Get the current time of this `CalendarAstronomer` object, represented as the number of milliseconds since 1/1/1970 AD 0:00 GMT (Gregorian).
`String`	`local(long localMillis)`
`void`	`setDate(Date date)`	Set the current date and time of this `CalendarAstronomer` object.
`void`	`setJulianDay(double jdn)`	Set the current date and time of this `CalendarAstronomer` object.
`void`	`setTime(long aTime)`	Set the current date and time of this `CalendarAstronomer` object.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - SIDEREAL_DAY
```
public static final double SIDEREAL_DAY
```
    The number of standard hours in one sidereal day. Approximately 24.93.
    
    See Also:
    
    Constant Field Values
  - SOLAR_DAY
```
public static final double SOLAR_DAY
```
    The number of sidereal hours in one mean solar day. Approximately 24.07.
    
    See Also:
    
    Constant Field Values
  - SYNODIC_MONTH
```
public static final double SYNODIC_MONTH
```
    The average number of solar days from one new moon to the next. This is the time it takes for the moon to return the same ecliptic longitude as the sun. It is longer than the sidereal month because the sun's longitude increases during the year due to the revolution of the earth around the sun. Approximately 29.53.
    
    See Also:
    
    SIDEREAL_MONTH, Constant Field Values
  - SIDEREAL_MONTH
```
public static final double SIDEREAL_MONTH
```
    The average number of days it takes for the moon to return to the same ecliptic longitude relative to the stellar background. This is referred to as the sidereal month. It is shorter than the synodic month due to the revolution of the earth around the sun. Approximately 27.32.
    
    See Also:
    
    SYNODIC_MONTH, Constant Field Values
  - TROPICAL_YEAR
```
public static final double TROPICAL_YEAR
```
    The average number number of days between successive vernal equinoxes. Due to the precession of the earth's axis, this is not precisely the same as the sidereal year. Approximately 365.24
    
    See Also:
    
    SIDEREAL_YEAR, Constant Field Values
  - SIDEREAL_YEAR
```
public static final double SIDEREAL_YEAR
```
    The average number of days it takes for the sun to return to the same position against the fixed stellar background. This is the duration of one orbit of the earth about the sun as it would appear to an outside observer. Due to the precession of the earth's axis, this is not precisely the same as the tropical year. Approximately 365.25.
    
    See Also:
    
    TROPICAL_YEAR, Constant Field Values
  - SECOND_MS
```
public static final int SECOND_MS
```
    The number of milliseconds in one second.
    
    See Also:
    
    Constant Field Values
  - MINUTE_MS
```
public static final int MINUTE_MS
```
    The number of milliseconds in one minute.
    
    See Also:
    
    Constant Field Values
  - HOUR_MS
```
public static final int HOUR_MS
```
    The number of milliseconds in one hour.
    
    See Also:
    
    Constant Field Values
  - DAY_MS
```
public static final long DAY_MS
```
    The number of milliseconds in one day.
    
    See Also:
    
    Constant Field Values
  - JULIAN_EPOCH_MS
```
public static final long JULIAN_EPOCH_MS
```
    The start of the julian day numbering scheme used by astronomers, which is 1/1/4713 BC (Julian), 12:00 GMT. This is given as the number of milliseconds since 1/1/1970 AD (Gregorian), a negative number. Note that julian day numbers and the Julian calendar are not the same thing. Also note that julian days start at noon, not midnight.
    
    See Also:
    
    Constant Field Values
  - VERNAL_EQUINOX
```
public static final com.ibm.icu.impl.CalendarAstronomer.SolarLongitude VERNAL_EQUINOX
```
    Constant representing the vernal equinox. For use with getSunTime. Note: In this case, "vernal" refers to the northern hemisphere's seasons.
  - SUMMER_SOLSTICE
```
public static final com.ibm.icu.impl.CalendarAstronomer.SolarLongitude SUMMER_SOLSTICE
```
    Constant representing the summer solstice. For use with getSunTime. Note: In this case, "summer" refers to the northern hemisphere's seasons.
  - AUTUMN_EQUINOX
```
public static final com.ibm.icu.impl.CalendarAstronomer.SolarLongitude AUTUMN_EQUINOX
```
    Constant representing the autumnal equinox. For use with getSunTime. Note: In this case, "autumn" refers to the northern hemisphere's seasons.
  - WINTER_SOLSTICE
```
public static final com.ibm.icu.impl.CalendarAstronomer.SolarLongitude WINTER_SOLSTICE
```
    Constant representing the winter solstice. For use with getSunTime. Note: In this case, "winter" refers to the northern hemisphere's seasons.
  - NEW_MOON
```
public static final com.ibm.icu.impl.CalendarAstronomer.MoonAge NEW_MOON
```
    Constant representing a new moon. For use with getMoonTime
  - FIRST_QUARTER
```
public static final com.ibm.icu.impl.CalendarAstronomer.MoonAge FIRST_QUARTER
```
    Constant representing the moon's first quarter. For use with getMoonTime
  - FULL_MOON
```
public static final com.ibm.icu.impl.CalendarAstronomer.MoonAge FULL_MOON
```
    Constant representing a full moon. For use with getMoonTime
  - LAST_QUARTER
```
public static final com.ibm.icu.impl.CalendarAstronomer.MoonAge LAST_QUARTER
```
    Constant representing the moon's last quarter. For use with getMoonTime
- Constructor Detail
  - CalendarAstronomer
```
public CalendarAstronomer()
```
    Construct a new CalendarAstronomer object that is initialized to the current date and time.
  - CalendarAstronomer
```
public CalendarAstronomer(Date d)
```
    Construct a new CalendarAstronomer object that is initialized to the specified date and time.
  - CalendarAstronomer
```
public CalendarAstronomer(long aTime)
```
    Construct a new CalendarAstronomer object that is initialized to the specified time. The time is expressed as a number of milliseconds since January 1, 1970 AD (Gregorian).
    
    See Also:
    
    Date.getTime()
  - CalendarAstronomer
```
public CalendarAstronomer(double longitude,
                          double latitude)
```
    Construct a new CalendarAstronomer object with the given latitude and longitude. The object's time is set to the current date and time.
    
    Parameters:
    
    longitude - The desired longitude, in degrees east of the Greenwich meridian.
    
    latitude - The desired latitude, in degrees. Positive values signify North, negative South.
    
    See Also:
    
    Date.getTime()
- Method Detail
  - setTime
```
public void setTime(long aTime)
```
    Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
    
    Parameters:
    
    aTime - the date and time, expressed as the number of milliseconds since 1/1/1970 0:00 GMT (Gregorian).
    
    See Also:
    
    setDate(java.util.Date), getTime()
  - setDate
```
public void setDate(Date date)
```
    Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
    
    Parameters:
    
    date - the time and date, expressed as a Date object.
    
    See Also:
    
    setTime(long), getDate()
  - setJulianDay
```
public void setJulianDay(double jdn)
```
    Set the current date and time of this CalendarAstronomer object. All astronomical calculations are performed based on this time setting.
    
    Parameters:
    
    jdn - the desired time, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT. Note that julian day numbers start at noon. To get the jdn for the corresponding midnight, subtract 0.5.
    
    See Also:
    
    getJulianDay(), JULIAN_EPOCH_MS
  - getTime
```
public long getTime()
```
    Get the current time of this CalendarAstronomer object, represented as the number of milliseconds since 1/1/1970 AD 0:00 GMT (Gregorian).
    
    See Also:
    
    setTime(long), getDate()
  - getDate
```
public Date getDate()
```
    Get the current time of this CalendarAstronomer object, represented as a Date object.
    
    See Also:
    
    setDate(java.util.Date), getTime()
  - getJulianDay
```
public double getJulianDay()
```
    Get the current time of this CalendarAstronomer object, expressed as a "julian day number", which is the number of elapsed days since 1/1/4713 BC (Julian), 12:00 GMT.
    
    See Also:
    
    setJulianDay(double), JULIAN_EPOCH_MS
  - getJulianCentury
```
public double getJulianCentury()
```
    Return this object's time expressed in julian centuries: the number of centuries after 1/1/1900 AD, 12:00 GMT
    
    See Also:
    
    getJulianDay()
  - getGreenwichSidereal
```
public double getGreenwichSidereal()
```
    Returns the current Greenwich sidereal time, measured in hours
  - getLocalSidereal
```
public double getLocalSidereal()
```
    Returns the current local sidereal time, measured in hours
  - eclipticToEquatorial
```
public final CalendarAstronomer.Equatorial eclipticToEquatorial(CalendarAstronomer.Ecliptic ecliptic)
```
    Convert from ecliptic to equatorial coordinates.
    
    Parameters:
    
    ecliptic - A point in the sky in ecliptic coordinates.
    
    Returns:
    
    The corresponding point in equatorial coordinates.
  - eclipticToEquatorial
```
public final CalendarAstronomer.Equatorial eclipticToEquatorial(double eclipLong,
                                                                double eclipLat)
```
    Convert from ecliptic to equatorial coordinates.
    
    Parameters:
    
    eclipLong - The ecliptic longitude
    
    eclipLat - The ecliptic latitude
    
    Returns:
    
    The corresponding point in equatorial coordinates.
  - eclipticToEquatorial
```
public final CalendarAstronomer.Equatorial eclipticToEquatorial(double eclipLong)
```
    Convert from ecliptic longitude to equatorial coordinates.
    
    Parameters:
    
    eclipLong - The ecliptic longitude
    
    Returns:
    
    The corresponding point in equatorial coordinates.
  - eclipticToHorizon
```
public CalendarAstronomer.Horizon eclipticToHorizon(double eclipLong)
```
  - getSunLongitude
```
public double getSunLongitude()
```
    The longitude of the sun at the time specified by this object. The longitude is measured in radians along the ecliptic from the "first point of Aries," the point at which the ecliptic crosses the earth's equatorial plane at the vernal equinox.
    Currently, this method uses an approximation of the two-body Kepler's equation for the earth and the sun. It does not take into account the perturbations caused by the other planets, the moon, etc.
  - getSunPosition
```
public CalendarAstronomer.Equatorial getSunPosition()
```
    The position of the sun at this object's current date and time, in equatorial coordinates.
  - getSunTime
```
public long getSunTime(double desired,
                       boolean next)
```
    Find the next time at which the sun's ecliptic longitude will have the desired value.
  - getSunTime
```
public long getSunTime(com.ibm.icu.impl.CalendarAstronomer.SolarLongitude desired,
                       boolean next)
```
    Find the next time at which the sun's ecliptic longitude will have the desired value.
  - getSunRiseSet
```
public long getSunRiseSet(boolean rise)
```
    Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set. NOTE: This method only works well if this object is set to a time near local noon. Because of variations between the local official time zone and the geographic longitude, the computation can flop over into an adjacent day if this object is set to a time near local midnight.
  - getMoonPosition
```
public CalendarAstronomer.Equatorial getMoonPosition()
```
    The position of the moon at the time set on this object, in equatorial coordinates.
  - getMoonAge
```
public double getMoonAge()
```
    The "age" of the moon at the time specified in this object. This is really the angle between the current ecliptic longitudes of the sun and the moon, measured in radians.
    
    See Also:
    
    getMoonPhase()
  - getMoonPhase
```
public double getMoonPhase()
```
    Calculate the phase of the moon at the time set in this object. The returned phase is a double in the range 0 <= phase < 1, interpreted as follows:
    
    0.00: New moon
    0.25: First quarter
    0.50: Full moon
    0.75: Last quarter
    See Also:
    
    getMoonAge()
  - getMoonTime
```
public long getMoonTime(double desired,
                        boolean next)
```
    Find the next or previous time at which the Moon's ecliptic longitude will have the desired value.
    
    Parameters:
    
    desired - The desired longitude.
    
    next - true if the next occurrance of the phase is desired, false for the previous occurrance.
  - getMoonTime
```
public long getMoonTime(com.ibm.icu.impl.CalendarAstronomer.MoonAge desired,
                        boolean next)
```
    Find the next or previous time at which the moon will be in the desired phase.
    
    Parameters:
    
    desired - The desired phase of the moon.
    
    next - true if the next occurrance of the phase is desired, false for the previous occurrance.
  - getMoonRiseSet
```
public long getMoonRiseSet(boolean rise)
```
    Returns the time (GMT) of sunrise or sunset on the local date to which this calendar is currently set.
  - local
```
public String local(long localMillis)
```

Class CalendarAstronomer

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

SIDEREAL_DAY

SOLAR_DAY

SYNODIC_MONTH

SIDEREAL_MONTH

TROPICAL_YEAR

SIDEREAL_YEAR

SECOND_MS

MINUTE_MS

HOUR_MS

DAY_MS

JULIAN_EPOCH_MS

VERNAL_EQUINOX

SUMMER_SOLSTICE

AUTUMN_EQUINOX

WINTER_SOLSTICE

NEW_MOON

FIRST_QUARTER

FULL_MOON

LAST_QUARTER

Constructor Detail

CalendarAstronomer

CalendarAstronomer

CalendarAstronomer

CalendarAstronomer

Method Detail

setTime

setDate

setJulianDay

getTime

getDate

getJulianDay

getJulianCentury

getGreenwichSidereal

getLocalSidereal

eclipticToEquatorial

eclipticToEquatorial

eclipticToEquatorial

eclipticToHorizon

getSunLongitude

getSunPosition

getSunTime

getSunTime

getSunRiseSet

getMoonPosition

getMoonAge

getMoonPhase

getMoonTime

getMoonTime

getMoonRiseSet

local