IslamicCalendar
public
class
IslamicCalendar
extends Calendar
java.lang.Object | ||
↳ | android.icu.util.Calendar | |
↳ | android.icu.util.IslamicCalendar |
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 three 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 and Saudi Arabia's Umm al-Qura calendar, however, are 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 astronomical calculations. At present, the approximations used in this class are fairly simplistic; they will be improved in later versions of the code.
Like the Islamic religious calendar, Umm al-Qura is also based on the sighting method of the crescent moon but is standardized by Saudi Arabia.
The fixed-cycle civil calendar is 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"
or "@calendar=islamic-umalqura"
.
See also:
Summary
Constants | |
---|---|
int |
DHU_AL_HIJJAH
Constant for Dhu al-Hijjah, the 12th month of the Islamic year. |
int |
DHU_AL_QIDAH
Constant for Dhu al-Qi'dah, the 11th month of the Islamic year. |
int |
JUMADA_1
Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year. |
int |
JUMADA_2
Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year. |
int |
MUHARRAM
Constant for Muharram, the 1st month of the Islamic year. |
int |
RABI_1
Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year. |
int |
RABI_2
Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year. |
int |
RAJAB
Constant for Rajab, the 7th month of the Islamic year. |
int |
RAMADAN
Constant for Ramadan, the 9th month of the Islamic year. |
int |
SAFAR
Constant for Safar, the 2nd month of the Islamic year. |
int |
SHABAN
Constant for Sha'ban, the 8th month of the Islamic year. |
int |
SHAWWAL
Constant for Shawwal, the 10th month of the Islamic year. |
Inherited constants |
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Inherited fields |
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Public constructors | |
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IslamicCalendar()
Constructs a default |
|
IslamicCalendar(TimeZone zone)
Constructs an |
|
IslamicCalendar(Locale aLocale)
Constructs an |
|
IslamicCalendar(ULocale locale)
Constructs an |
|
IslamicCalendar(TimeZone zone, Locale aLocale)
Constructs an |
|
IslamicCalendar(TimeZone zone, ULocale locale)
Constructs an |
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IslamicCalendar(Date date)
Constructs an |
|
IslamicCalendar(int year, int month, int date)
Constructs an |
|
IslamicCalendar(int year, int month, int date, int hour, int minute, int second)
Constructs an |
Public methods | |
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IslamicCalendar.CalculationType
|
getCalculationType()
gets the calculation type for this calendar. |
String
|
getType()
[icu] Returns the calendar type name string for this Calendar object. |
void
|
setCalculationType(IslamicCalendar.CalculationType type)
sets the calculation type for this calendar. |
Protected methods | |
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void
|
handleComputeFields(int julianDay)
Override Calendar to compute several fields specific to the Islamic calendar system. |
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. |
int
|
handleGetExtendedYear()
Returns the extended year defined by the current fields. |
int
|
handleGetLimit(int field, int limitType)
Subclass API for defining limits of different types. |
int
|
handleGetMonthLength(int extendedYear, int month)
Return the length (in days) of the given month. |
int
|
handleGetYearLength(int extendedYear)
Return the number of days in the given Islamic year |
Inherited methods | |
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Constants
DHU_AL_HIJJAH
public static final int DHU_AL_HIJJAH
Constant for Dhu al-Hijjah, the 12th month of the Islamic year.
Constant Value: 11 (0x0000000b)
DHU_AL_QIDAH
public static final int DHU_AL_QIDAH
Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.
Constant Value: 10 (0x0000000a)
JUMADA_1
public static final int JUMADA_1
Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.
Constant Value: 4 (0x00000004)
JUMADA_2
public static final int JUMADA_2
Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.
Constant Value: 5 (0x00000005)
MUHARRAM
public static final int MUHARRAM
Constant for Muharram, the 1st month of the Islamic year.
Constant Value: 0 (0x00000000)
RABI_1
public static final int RABI_1
Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.
Constant Value: 2 (0x00000002)
RABI_2
public static final int RABI_2
Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.
Constant Value: 3 (0x00000003)
RAJAB
public static final int RAJAB
Constant for Rajab, the 7th month of the Islamic year.
Constant Value: 6 (0x00000006)
RAMADAN
public static final int RAMADAN
Constant for Ramadan, the 9th month of the Islamic year.
Constant Value: 8 (0x00000008)
SAFAR
public static final int SAFAR
Constant for Safar, the 2nd month of the Islamic year.
Constant Value: 1 (0x00000001)
SHABAN
public static final int SHABAN
Constant for Sha'ban, the 8th month of the Islamic year.
Constant Value: 7 (0x00000007)
SHAWWAL
public static final int SHAWWAL
Constant for Shawwal, the 10th month of the Islamic year.
Constant Value: 9 (0x00000009)
Public constructors
IslamicCalendar
public IslamicCalendar ()
Constructs a default IslamicCalendar
using the current time
in the default time zone with the default FORMAT
locale.
See also:
IslamicCalendar
public IslamicCalendar (TimeZone zone)
Constructs an IslamicCalendar
based on the current time
in the given time zone with the default FORMAT
locale.
Parameters | |
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zone |
TimeZone : the given time zone. |
See also:
IslamicCalendar
public IslamicCalendar (Locale aLocale)
Constructs an IslamicCalendar
based on the current time
in the default time zone with the given locale.
Parameters | |
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aLocale |
Locale : the given locale. |
IslamicCalendar
public IslamicCalendar (ULocale locale)
Constructs an IslamicCalendar
based on the current time
in the default time zone with the given locale.
Parameters | |
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locale |
ULocale : the given ulocale. |
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 | |
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zone |
TimeZone : the given time zone. |
aLocale |
Locale : the given locale. |
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 | |
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zone |
TimeZone : the given time zone. |
locale |
ULocale : the given ulocale. |
IslamicCalendar
public IslamicCalendar (Date date)
Constructs an IslamicCalendar
with the given date set
in the default time zone with the default FORMAT
locale.
Parameters | |
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date |
Date : The date to which the new calendar is set. |
See also:
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 FORMAT
locale.
Parameters | |
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year |
int : the value used to set the YEAR time field in the calendar. |
month |
int : 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 |
int : the value used to set the DATE time field in the calendar. |
See also:
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 FORMAT
locale.
Parameters | |
---|---|
year |
int : the value used to set the YEAR time field in the calendar. |
month |
int : 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 |
int : the value used to set the DATE time field in the calendar. |
hour |
int : the value used to set the HOUR_OF_DAY time field
in the calendar. |
minute |
int : the value used to set the MINUTE time field
in the calendar. |
second |
int : the value used to set the SECOND time field
in the calendar. |
See also:
Public methods
getCalculationType
public IslamicCalendar.CalculationType getCalculationType ()
gets the calculation type for this calendar.
Returns | |
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IslamicCalendar.CalculationType |
getType
public String getType ()
[icu] Returns the calendar type name string for this Calendar object. The returned string is the legacy ICU calendar attribute value, for example, "gregorian" or "japanese".
See type="old type name" for the calendar attribute of locale IDs at http://www.unicode.org/reports/tr35/#Key_Type_Definitions
Returns | |
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String |
legacy calendar type name string |
setCalculationType
public void setCalculationType (IslamicCalendar.CalculationType type)
sets the calculation type for this calendar.
Parameters | |
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type |
IslamicCalendar.CalculationType |
Protected methods
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
Parameters | |
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julianDay |
int |
handleComputeMonthStart
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. Subclasses should override this method to implement their calendar system.
Parameters | |
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eyear |
int : the extended year |
month |
int : the zero-based month, or 0 if useMonth is false |
useMonth |
boolean : 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 | |
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int |
the Julian day number of the day before the first day of the given month and year |
handleGetExtendedYear
protected int handleGetExtendedYear ()
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.
Returns | |
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int |
the extended year |
handleGetLimit
protected int handleGetLimit (int field, int limitType)
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
Parameters | |
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field |
int : one of the above field numbers |
limitType |
int : one of MINIMUM , GREATEST_MINIMUM ,
LEAST_MAXIMUM , or MAXIMUM |
Returns | |
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int |
handleGetMonthLength
protected int handleGetMonthLength (int extendedYear, int month)
Return the length (in days) of the given month.
Parameters | |
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extendedYear |
int : The hijri year |
month |
int : The hijri month, 0-based |
Returns | |
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int |
handleGetYearLength
protected int handleGetYearLength (int extendedYear)
Return the number of days in the given Islamic year
Parameters | |
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extendedYear |
int |
Returns | |
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int |