A group of Islamic calendar algorithm defined by simple rules without astronomical calculation is called tabular Islamic calendars. In this proposal, we categorize all of sighting based Islamic calendar as a group of religious calendars.īecause the religious calendar date is not determined precisely, there were several algorithms developed for non-religious purposes. This traditional practice is still followed in the majority of Muslim countries. Because of the sighting of the hilal is affected by various factors not predictable (clouds or brightness of the sky, geographic location and others), it is impossible to determine dates by calculation. Traditionally, the first day of month is the day of the first sighting of the hilal (crescent moon) shortly after sunset. So they proposed to add a few islamic calendar types - one of Um al-Qura, one for Saudi Arabia sighting. JSR-310 folks want to identify calendar type using BCP 47 locale extension. Recently, JSR-310 (formerly - Joda Time) was approved and the whole new date/time package will be integrated into Java 8. MS's UmAlQuraCalendar supports Umm al-Qura calendar introduced by Saudi Arabia. Note: The link in the above reference page indicates MS's "Kuwaiti Algorithm" is type I (using Intercalary years with 355 days in each 30-year cycle with 2,5,7,10,13,15,18,21,24,26 &29), but HijriCalendar class on. My understanding is that MS's implementation just use CE 622 July 15 (Julian) as the epoch date, that is one day before the ICU's implementation. I compared MS's "HijriCalendar" with ICU's "islamic-civil" calendar side by side and I found ICU's islamic-civil is always one day after the MS's HijriCalendar. According to this page, the algorithm used by MS's "HijriCalendar" is nothing more than simple arithmetic one, that is pretty similar to ICU's "islamic-civil" calendar. The former was introduced a long time ago. NET, these are named HijriCalendar and UmAlQuraCalendar. Microsoft also provides two calendar types. The intent of latter is to provider better approximation of Hijri calendar actually used by countries, but it's not quite perfect. ICU's "islamic" (astronomical) is based on astronomical calculation of moon phase based on a certain location. In this book, "civil" calendar uses the simple arithmetical algorithm based on CE 622 July 16 Friday (Julian calendar). They originally came from the ICU implementations that seems to be largely influenced by the book - Calendrical Calculations, Nachum Dershowitz, Edward M. In CLDR, we have two Islamic calendar types available - "islamic" (astronomical?) and "islamic-civil".
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