Java Doc for IslamicChronology.java in  » Development » Joda-Time » org » joda » time » chrono » Java Source Code / Java DocumentationJava Source Code and Java Documentation

This calendar is a lunar calendar with a shorter year than ISO. Year 1 in the Islamic calendar began on July 16, 622 CE (Julian), thus Islamic years do not begin at the same time as Julian years. This chronology is not proleptic, as it does not allow dates before the first Islamic year.

There are two basic forms of the Islamic calendar, the tabular and the observed. The observed form cannot easily be used by computers as it relies on human observation of the new moon. The tabular calendar, implemented here, is an arithmetical approximation of the observed form that follows relatively simple rules.

The tabular form of the calendar defines 12 months of alternately 30 and 29 days. The last month is extended to 30 days in a leap year. Leap years occur according to a 30 year cycle. There are four recognised patterns of leap years in the 30 year cycle:

 Years 2, 5, 7, 10, 13, 15, 18, 21, 24, 26 & 29 - 15-based, used by Microsoft
 Years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 & 29 - 16-based, most commonly used
 Years 2, 5, 8, 10, 13, 16, 19, 21, 24, 27 & 29 - Indian
 Years 2, 5, 8, 11, 13, 16, 19, 21, 24, 27 & 30 - Habash al-Hasib
 

This implementation defines a day as midnight to midnight exactly as per the ISO chronology. This correct start of day is at sunset on the previous day, however this cannot readily be modelled and has been ignored.

IslamicChronology is thread-safe and immutable.
See Also:    Wikipedia
author:
   Stephen Colebourne
since:
   1.2