Bīrūnī, Muḥammad ibn Aḥmad, Alberuni's India (v. 2)

(London :  Kegan Paul, Trench, Trübner & Co.,  1910.)



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  Page 48  


Method of
the Arabic
book Al-

solar days. Thereby we get lunar days, viz. 135,780.
We write down this number below the three numbers,
multiply it by II, and add 497 to the product. Thus
we get the sum 1,494,077. We write this number
below the four numbers, and divide it by 111,573. The
quotient is 13, and the remainder, i.e. 43,628, is dis¬
regarded. We subtract the quotient from the middle
number. Thus we get the remainder, 1,494,064. We
divide it by 703. The quotient is 2125, and the re¬
mainder, i.e. ctvctma, is iff. We subtract the quotient
from the lunar days, and get the remainder 133,655.
These are the civil days which we want to find. Divid¬
ing them by 7, we get 4 as remainder. Therefore the
1st of the month Caitra of the gauge-year falls on a

The epoch of the era of Yazdajird precedes the epoch
of this era (v. era nr. 5, p. 7) by 11,968 days. There¬
fore the sum of the days of the era of Yazdajird up to
our gauge-date is 145,623 days. Dividing them by the
Persian year and months, we get as the.corresponding
Persian date the yectr of Yazdajird 399, the i8th Isfan-
ddrmadh. Before the ctdhimdsa month becomes com¬
plete with 30 days, there must still elapse five ghctti,
i.e. two hours. In consequence, the year is a leap year,
and Caitra is the month which is reckoned twice in it.

The following is the method of the canon or calendar
Al-arkand, according to a bad translation: "If you
want to know the Arkctnd, i.e. ahargana, take 90, mul¬
tiply it by 6, add to the product 8, and the years of
the realm of Sindh, i.e. the time till the month Safar,
A.H. 117, which corresponds to the Caitra of the year
109. Subtract therefrom 587, and the remainder re¬
presents the years of the Shakh.

An easier method is the following : " Take the com¬
plete years of the Aera Yctzdagirdi, and subtract there¬
from 33. The remainder represents the years of the
Shctkh.    Or you may also begin with the original ninety
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