com.ibm.icu.util
Class IslamicCalendar

java.lang.Object
  com.ibm.icu.util.Calendar
      com.ibm.icu.util.IslamicCalendar

All Implemented Interfaces:

Serializable, Cloneable, Comparable<Calendar>

public class IslamicCalendar
extends Calendar

IslamicCalendar is a subclass of Calendar that that implements the Islamic civil and religious calendars. It is used as the civil calendar in most of the Arab world and the liturgical calendar of the Islamic faith worldwide. This calendar is also known as the "Hijri" calendar, since it starts at the time of Mohammed's emigration (or "hijra") to Medinah on Thursday, July 15, 622 AD (Julian).

The Islamic calendar is strictly lunar, and thus an Islamic year of twelve lunar months does not correspond to the solar year used by most other calendar systems, including the Gregorian. An Islamic year is, on average, about 354 days long, so each successive Islamic year starts about 11 days earlier in the corresponding Gregorian year.

Each month of the calendar starts when the new moon's crescent is visible at sunset. However, in order to keep the time fields in this class synchronized with those of the other calendars and with local clock time, we treat days and months as beginning at midnight, roughly 6 hours after the corresponding sunset.

There are two main variants of the Islamic calendar in existence. The first is the civil calendar, which uses a fixed cycle of alternating 29- and 30-day months, with a leap day added to the last month of 11 out of every 30 years. This calendar is easily calculated and thus predictable in advance, so it is used as the civil calendar in a number of Arab countries. This is the default behavior of a newly-created IslamicCalendar object.

The Islamic religious calendar, however, is based on the observation of the crescent moon. It is thus affected by the position at which the observations are made, seasonal variations in the time of sunset, the eccentricities of the moon's orbit, and even the weather at the observation site. This makes it impossible to calculate in advance, and it causes the start of a month in the religious calendar to differ from the civil calendar by up to three days.

Using astronomical calculations for the position of the sun and moon, the moon's illumination, and other factors, it is possible to determine the start of a lunar month with a fairly high degree of certainty. However, these calculations are extremely complicated and thus slow, so most algorithms, including the one used here, are only approximations of the true astronical calculations. At present, the approximations used in this class are fairly simplistic; they will be improved in later versions of the code.

The setCivil method determines which approach is used to determine the start of a month. By default, the fixed-cycle civil calendar is used. However, if setCivil(false) is called, an approximation of the true lunar calendar will be used.

This class should not be subclassed.

IslamicCalendar usually should be instantiated using Calendar.getInstance(ULocale) passing in a ULocale with the tag "@calendar=islamic" or "@calendar=islamic-civil".

Author:

Laura Werner, Alan Liu

See Also:

GregorianCalendar, Calendar, Serialized Form

Status:

Stable ICU 2.8.

Nested Class Summary

Nested classes/interfaces inherited from class com.ibm.icu.util.Calendar

Calendar.FormatConfiguration

Field Summary

static int	DHU_AL_HIJJAH Constant for Dhu al-Hijjah, the 12th month of the Islamic year.
static int	DHU_AL_QIDAH Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.
static int	JUMADA_1 Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.
static int	JUMADA_2 Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.
static int	MUHARRAM Constant for Muharram, the 1st month of the Islamic year.
static int	RABI_1 Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.
static int	RABI_2 Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.
static int	RAJAB Constant for Rajab, the 7th month of the Islamic year.
static int	RAMADAN Constant for Ramadan, the 9th month of the Islamic year.
static int	SAFAR Constant for Safar, the 2nd month of the Islamic year.
static int	SHABAN Constant for Sha'ban, the 8th month of the Islamic year.
static int	SHAWWAL Constant for Shawwal, the 10th month of the Islamic year.

Fields inherited from class com.ibm.icu.util.Calendar

AM, AM_PM, APRIL, AUGUST, BASE_FIELD_COUNT, DATE, DAY_OF_MONTH, DAY_OF_WEEK, DAY_OF_WEEK_IN_MONTH, DAY_OF_YEAR, DECEMBER, DOW_LOCAL, DST_OFFSET, EPOCH_JULIAN_DAY, ERA, EXTENDED_YEAR, FEBRUARY, FRIDAY, GREATEST_MINIMUM, HOUR, HOUR_OF_DAY, INTERNALLY_SET, IS_LEAP_MONTH, JAN_1_1_JULIAN_DAY, JANUARY, JULIAN_DAY, JULY, JUNE, LEAST_MAXIMUM, MARCH, MAX_DATE, MAX_FIELD_COUNT, MAX_JULIAN, MAX_MILLIS, MAXIMUM, MAY, MILLISECOND, MILLISECONDS_IN_DAY, MIN_DATE, MIN_JULIAN, MIN_MILLIS, MINIMUM, MINIMUM_USER_STAMP, MINUTE, MONDAY, MONTH, NOVEMBER, OCTOBER, ONE_DAY, ONE_HOUR, ONE_MINUTE, ONE_SECOND, ONE_WEEK, PM, RESOLVE_REMAP, SATURDAY, SECOND, SEPTEMBER, SUNDAY, THURSDAY, TUESDAY, UNDECIMBER, UNSET, WEDNESDAY, WEEK_OF_MONTH, WEEK_OF_YEAR, WEEKDAY, WEEKEND, WEEKEND_CEASE, WEEKEND_ONSET, YEAR, YEAR_WOY, ZONE_OFFSET

Constructor Summary

IslamicCalendar()
Constructs a default IslamicCalendar using the current time in the default time zone with the default locale.

IslamicCalendar(Date date)
Constructs an IslamicCalendar with the given date set in the default time zone with the default locale.

IslamicCalendar(int year, int month, int date)
Constructs an IslamicCalendar with the given date set in the default time zone with the default locale.

IslamicCalendar(int year, int month, int date, int hour, int minute, int second)
Constructs an IslamicCalendar with the given date and time set for the default time zone with the default locale.

IslamicCalendar(Locale aLocale)
Constructs an IslamicCalendar based on the current time in the default time zone with the given locale.

IslamicCalendar(TimeZone zone)
Constructs an IslamicCalendar based on the current time in the given time zone with the default locale.

IslamicCalendar(TimeZone zone, Locale aLocale)
Constructs an IslamicCalendar based on the current time in the given time zone with the given locale.

IslamicCalendar(TimeZone zone, ULocale locale)
Constructs an IslamicCalendar based on the current time in the given time zone with the given locale.

IslamicCalendar(ULocale locale)
Constructs an IslamicCalendar based on the current time in the default time zone with the given locale.

Method Summary

String	getType() [icu] Returns the current Calendar type.
protected void	handleComputeFields(int julianDay) Override Calendar to compute several fields specific to the Islamic calendar system.
protected int	handleComputeMonthStart(int eyear, int month, boolean useMonth) Returns the Julian day number of day before the first day of the given month in the given extended year.
protected int	handleGetExtendedYear() Returns the extended year defined by the current fields.
protected int	handleGetLimit(int field, int limitType) Subclass API for defining limits of different types.
protected int	handleGetMonthLength(int extendedYear, int month) Return the length (in days) of the given month.
protected int	handleGetYearLength(int extendedYear) Return the number of days in the given Islamic year
boolean	isCivil() Returns true if this object is using the fixed-cycle civil calendar, or false if using the religious, astronomical calendar.
void	setCivil(boolean beCivil) Determines whether this object uses the fixed-cycle Islamic civil calendar or an approximation of the religious, astronomical calendar.

Methods inherited from class com.ibm.icu.util.Calendar

add, after, before, clear, clear, clone, compareTo, complete, computeFields, computeGregorianFields, computeGregorianMonthStart, computeJulianDay, computeMillisInDay, computeTime, computeZoneOffset, equals, fieldDifference, fieldName, floorDivide, floorDivide, floorDivide, floorDivide, get, getActualMaximum, getActualMinimum, getAvailableLocales, getAvailableULocales, getDateTimeFormat, getDateTimeFormat, getDateTimePattern, getDayOfWeekType, getDefaultDayInMonth, getDefaultMonthInYear, getDisplayName, getDisplayName, getFieldCount, getFieldResolutionTable, getFirstDayOfWeek, getGreatestMinimum, getGregorianDayOfMonth, getGregorianDayOfYear, getGregorianMonth, getGregorianYear, getInstance, getInstance, getInstance, getInstance, getInstance, getInstance, getKeywordValuesForLocale, getLeastMaximum, getLimit, getLocale, getMaximum, getMinimalDaysInFirstWeek, getMinimum, getStamp, getTime, getTimeInMillis, getTimeZone, getWeekendTransition, gregorianMonthLength, gregorianPreviousMonthLength, handleComputeJulianDay, handleCreateFields, handleGetDateFormat, handleGetDateFormat, handleGetDateFormat, handleGetDateFormat, hashCode, internalGet, internalGet, internalGetTimeInMillis, internalSet, isEquivalentTo, isGregorianLeapYear, isLenient, isSet, isWeekend, isWeekend, julianDayToDayOfWeek, julianDayToMillis, millisToJulianDay, newerField, newestStamp, pinField, prepareGetActual, resolveFields, roll, roll, set, set, set, set, setFirstDayOfWeek, setLenient, setMinimalDaysInFirstWeek, setTime, setTimeInMillis, setTimeZone, toString, validateField, validateField, validateFields, weekNumber, weekNumber

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

MUHARRAM

public static final int MUHARRAM

Constant for Muharram, the 1st month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

SAFAR

public static final int SAFAR

Constant for Safar, the 2nd month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

RABI_1

public static final int RABI_1

Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

RABI_2

public static final int RABI_2

Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

JUMADA_1

public static final int JUMADA_1

Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

JUMADA_2

public static final int JUMADA_2

Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

RAJAB

public static final int RAJAB

Constant for Rajab, the 7th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

SHABAN

public static final int SHABAN

Constant for Sha'ban, the 8th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

RAMADAN

public static final int RAMADAN

Constant for Ramadan, the 9th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

SHAWWAL

public static final int SHAWWAL

Constant for Shawwal, the 10th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

DHU_AL_QIDAH

public static final int DHU_AL_QIDAH

Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

DHU_AL_HIJJAH

public static final int DHU_AL_HIJJAH

Constant for Dhu al-Hijjah, the 12th month of the Islamic year.

See Also:

Constant Field Values

Status:

Stable ICU 2.8.

Constructor Detail

IslamicCalendar

public IslamicCalendar()

Constructs a default IslamicCalendar using the current time in the default time zone with the default locale.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(TimeZone zone)

Constructs an IslamicCalendar based on the current time in the given time zone with the default locale.

Parameters:

zone - the given time zone.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(Locale aLocale)

Constructs an IslamicCalendar based on the current time in the default time zone with the given locale.

Parameters:

aLocale - the given locale.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(ULocale locale)

Constructs an IslamicCalendar based on the current time in the default time zone with the given locale.

Parameters:

locale - the given ulocale.

Status:

Stable ICU 3.2.

IslamicCalendar

public IslamicCalendar(TimeZone zone,
                       Locale aLocale)

Constructs an IslamicCalendar based on the current time in the given time zone with the given locale.

Parameters:

zone - the given time zone.

aLocale - the given locale.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(TimeZone zone,
                       ULocale locale)

Constructs an IslamicCalendar based on the current time in the given time zone with the given locale.

Parameters:

zone - the given time zone.

locale - the given ulocale.

Status:

Stable ICU 3.2.

IslamicCalendar

public IslamicCalendar(Date date)

Constructs an IslamicCalendar with the given date set in the default time zone with the default locale.

Parameters:

date - The date to which the new calendar is set.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(int year,
                       int month,
                       int date)

Constructs an IslamicCalendar with the given date set in the default time zone with the default locale.

Parameters:

year - the value used to set the YEAR time field in the calendar.

month - the value used to set the MONTH time field in the calendar. Note that the month value is 0-based. e.g., 0 for Muharram.

date - the value used to set the DATE time field in the calendar.

Status:

Stable ICU 2.8.

IslamicCalendar

public IslamicCalendar(int year,
                       int month,
                       int date,
                       int hour,
                       int minute,
                       int second)

Constructs an IslamicCalendar with the given date and time set for the default time zone with the default locale.

Parameters:

year - the value used to set the YEAR time field in the calendar.

month - the value used to set the MONTH time field in the calendar. Note that the month value is 0-based. e.g., 0 for Muharram.

date - the value used to set the DATE time field in the calendar.

hour - the value used to set the HOUR_OF_DAY time field in the calendar.

minute - the value used to set the MINUTE time field in the calendar.

second - the value used to set the SECOND time field in the calendar.

Status:

Stable ICU 2.8.

Method Detail

setCivil

public void setCivil(boolean beCivil)

Determines whether this object uses the fixed-cycle Islamic civil calendar or an approximation of the religious, astronomical calendar.

Parameters:

beCivil - true to use the civil calendar, false to use the astronomical calendar.

Status:

Stable ICU 2.8.

isCivil

public boolean isCivil()

Returns true if this object is using the fixed-cycle civil calendar, or false if using the religious, astronomical calendar.

Status:

Stable ICU 2.8.

handleGetLimit

protected int handleGetLimit(int field,
                             int limitType)

Description copied from class: Calendar

Subclass API for defining limits of different types. Subclasses must implement this method to return limits for the following fields:

ERA
 YEAR
 MONTH
 WEEK_OF_YEAR
 WEEK_OF_MONTH
 DAY_OF_MONTH
 DAY_OF_YEAR
 DAY_OF_WEEK_IN_MONTH
 YEAR_WOY
 EXTENDED_YEAR

Specified by:

handleGetLimit in class Calendar

Parameters:

field - one of the above field numbers

limitType - one of MINIMUM, GREATEST_MINIMUM, LEAST_MAXIMUM, or MAXIMUM

Status:

Stable ICU 2.8.

handleGetMonthLength

protected int handleGetMonthLength(int extendedYear,
                                   int month)

Return the length (in days) of the given month.

Overrides:

handleGetMonthLength in class Calendar

Parameters:

extendedYear - The hijri year

month - The hijri month, 0-based

Status:

Stable ICU 2.8.

handleGetYearLength

protected int handleGetYearLength(int extendedYear)

Return the number of days in the given Islamic year

Overrides:

handleGetYearLength in class Calendar

Status:

Stable ICU 2.8.

handleComputeMonthStart

protected int handleComputeMonthStart(int eyear,
                                      int month,
                                      boolean useMonth)

Description copied from class: Calendar

Returns the Julian day number of day before the first day of the given month in the given extended year. Subclasses should override this method to implement their calendar system.

Specified by:

handleComputeMonthStart in class Calendar

Parameters:

eyear - the extended year

month - the zero-based month, or 0 if useMonth is false

useMonth - if false, compute the day before the first day of the given year, otherwise, compute the day before the first day of the given month

Returns:

the Julian day number of the day before the first day of the given month and year

Status:

Stable ICU 2.8.

handleGetExtendedYear

protected int handleGetExtendedYear()

Description copied from class: Calendar

Returns the extended year defined by the current fields. This will use the EXTENDED_YEAR field or the YEAR and supra-year fields (such as ERA) specific to the calendar system, depending on which set of fields is newer.

Specified by:

handleGetExtendedYear in class Calendar

Returns:

the extended year

Status:

Stable ICU 2.8.

handleComputeFields

protected void handleComputeFields(int julianDay)

Override Calendar to compute several fields specific to the Islamic calendar system. These are:

• ERA
• YEAR
• MONTH
• DAY_OF_MONTH
• DAY_OF_YEAR
• EXTENDED_YEAR

The DAY_OF_WEEK and DOW_LOCAL fields are already set when this method is called. The getGregorianXxx() methods return Gregorian calendar equivalents for the given Julian day.

Overrides:

handleComputeFields in class Calendar

Status:

Stable ICU 2.8.

getType

public String getType()

[icu] Returns the current Calendar type. Note, in 3.0 this function will return 'gregorian' in Calendar to emulate legacy behavior

Overrides:

getType in class Calendar

Returns:

type of calendar (gregorian, etc)

Status:

Stable ICU 3.8.