This template gives the Julian year(s) for a given Hijri year. Use this template only in cases where Hijri year is known, but not the month or day. This situation is common for the birth/death dates of medieval people. The given AH year usually results in two possible CE years.
The arithmetical or tabular calendar was introduced by Muslim astronomers in the 9th century CE to predict the start of each month in the Islamic lunar calendar. The months in the tabular Islamic calendar are assumed to be alternately 30 and 29 days in length, resulting in a normal calendar year of 354 days (sanā basīta). In order to keep the calendar in step with the lunar phases, every two or three years an extra day is added to the last month of the year, resulting in a calendar year of 355 days (sanā kabīsa). According to the most commonly adopted method, intercalary days are added 11 times in each 30-year cycle. Four slightly different intercalary schemes have been described in the literature. The Fātimid calendar used by this template (also known as the Misri or Bohra calendar) inserts intercalary days in years 2, 5, 8, 10, 13, 16, 19, 21, 24, 27, and 29.
Of each intercalary scheme two variants are possible, depending on whether the epoch of the Islamic calendar (1 Muharram, 1 AH) is assumed to be 15 July 622 CE (known as the "astronomical" or "Thursday" epoch, Julian day 1948439) or 16 July 622 CE (the "civil" or "Friday" epoch, Julian day 1948440).
This template's calculations do not take into account the Gregorian calendar reform of 1582, but:
- This template is intended for medieval dates before AH 989 (1581/1582). For later dates, the exact dates will typically be known.
- For most years post-1582 the result will still be accurate.