com.ibm.icu.util
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 {@link #setCivil 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
{@link com.ibm.icu.util.Calendar#getInstance(ULocale)} passing in a ULocale
with the tag "@calendar=islamic"
or "@calendar=islamic-civil"
.
See Also: GregorianCalendar
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Field Summary | |
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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. |
Constructor Summary | |
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IslamicCalendar()
Constructs a default IslamicCalendar using the current time
in the default time zone with the default locale. | |
IslamicCalendar(TimeZone zone)
Constructs an IslamicCalendar based on the current time
in the given 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(ULocale locale)
Constructs an IslamicCalendar based on the current time
in the default time zone with the given 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(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.
|
Method Summary | |
---|---|
String | getType()
Return 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) |
protected int | handleGetExtendedYear() |
protected int | handleGetLimit(int field, int limitType) |
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.
|
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IslamicCalendar
using the current time
in the default time zone with the default locale.UNKNOWN: ICU 2.8
IslamicCalendar
based on the current time
in the given time zone with the default locale.Parameters: zone the given time zone.
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IslamicCalendar
based on the current time
in the default time zone with the given locale.
Parameters: aLocale the given locale.
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IslamicCalendar
based on the current time
in the default time zone with the given locale.
Parameters: locale the given ulocale.
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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.
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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.
UNKNOWN: ICU 3.2 This API might change or be removed in a future release.
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.
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IslamicCalendar
with the given date set
in the default time zone with the default locale.
Parameters: year the value used to set the {@link #YEAR YEAR} time field in the calendar. month the value used to set the {@link #MONTH 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 {@link #DATE DATE} time field in the calendar.
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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 {@link #YEAR YEAR} time field in the calendar. month the value used to set the {@link #MONTH 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 {@link #DATE DATE} time field in the calendar. hour the value used to set the {@link #HOUR_OF_DAY HOUR_OF_DAY} time field in the calendar. minute the value used to set the {@link #MINUTE MINUTE} time field in the calendar. second the value used to set the {@link #SECOND SECOND} time field in the calendar.
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Returns: type of calendar (gregorian, etc.)
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Parameters: extendedYear The hijri year month The hijri month, 0-based
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true
if this object is using the fixed-cycle civil
calendar, or false
if using the religious, astronomical
calendar.UNKNOWN: ICU 2.8
Parameters: beCivil true
to use the civil calendar,
false
to use the astronomical calendar.
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