Islamic calendar | converting hijri to gregorian date or vice versa
Conversions may be made by using the
This table may be extended since every nineteen years the Muslim month number increases by seven. When it goes above twelve, subtract twelve and add one to the year AH. From 412 AD/CE to 632 AD/CE inclusive the month number is 1 and the calculation gives the month correct to a month or so. 622 AD/CE corresponds to BH 1 and AH 1. For earlier years, year BH = (623 or 622) – year AD/CE).
An example calculation: What is the civil date and year AH of the first day of the first month in the year 20875 AD/CE?
We first find the Muslim month number corresponding to the first month of the Jewish year which begins in 20874 AD/CE. Dividing 20874 by 19 gives quotient 1098 and remainder 12. Dividing 2026 by 19 gives quotient 106 and remainder 12. 2026 is chosen because it gives the same remainder on division by 19 as 20874. The two years are therefore (1098–106)=992×19 years apart. The Muslim month number corresponding to the first Jewish month is therefore 992×7=6944 higher than in 2026. To convert into years and months divide by twelve – 6944/12=578 years and 8 months. Adding, we get 1447y 10m + 20874y – 2026y + 578y 8m = 20874y 6m. Therefore, the first month of the Jewish year beginning in 20874 AD/CE corresponds to the sixth month of the Muslim year AH 20874. The worked example in
A reading of the section which follows will show that the year AH 20875 is wholly contained within the year 20875 AD/CE, also that in the Gregorian calendar this correspondence will occur one year earlier. The reason for the discrepancy is that the Gregorian year (like the Julian, though less so) is slightly too long, so the Gregorian date for a given AH date will be earlier and the Muslim calendar catches up sooner.
An Islamic year will be entirely within a Gregorian year of the same number in the year 20874, after which year the number of the Islamic year will always be greater than the number of the concurrent civil year. The Islamic calendar year of 1429 occurred entirely within the civil calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 civil years). More are listed here:
|Islamic year within civil year|
Because a Hijri or Islamic lunar year is between 10 and 12 days shorter than a civil year, it begins 10–12 days earlier in the civil year following the civil year in which the previous Hijri year began. Once every 33 or 34 Hijri years, or once every 32 or 33 civil years, the beginning of a Hijri year (1 Muharram) coincides with one of the first ten days of January. Subsequent Hijri New Years move backward through the civil year back to the beginning of January again, passing through each civil month from December to January.