ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

UNITS OF TIME 297 Addendum : The mean lunar day (madhyama tithi) may, however, differ from a true lunar day (spaṣṭa tithi) by one, so that the ahargaṇa obtained by the above process may sometimes be in excess or defect by one. To test whether the ahargaṇa (obtained by the above process) is correct, it is divided by seven and the remainder counted with Friday. If this leads to the day of calculation, the ahargaṇa is correct; if it leads to the preceding day, the ahargaṇa is in defect; and if that leads to the succeeding day, the ahargaṇa is in excess. When the ahargaṇa is found to be in defect, it is increased by one; when it is found to be in excess, it is diminished by one. (K.S. Shukla : MBh. p. 4-5) Example—Calculate the ahargaṇa on October 1,1965. From Indian Calendar we find that October 1,1965 falls on Friday. 7th lunar day (tithi) in the light half of the 7th month Āśvina in the Saka year 1887 (elapsed). Let us proceed as follows : Adding 3,179 to 1,887. we get 5,066. (1) Multiplying this by 12 and adding 6 (i. e. the number of lunar months elapsed since the beginning of Caitra) we get 60,798. ... ... (2). Multiplying this by 1,593,336 and dividing the product by 51,840,000, we get 1,868 as quotient. (The remainder is discarded as unnecessary) (3) Adding this number (i.e. 1,868) to the previous one (i.e.) 60,798) we get 62,666. (4) Multiplying this by 30 and adding 6 (i.e. the number of lunar days elapsed since the beginning of the current month) to the product, we get 1,879,986. (5) Multiplying this by 25,082,580 and dividing the product by 1,603,000,080, we get 29,416 as the quotient. (The remainder is discarded as not necessary). (6) Subtracting this number (i.e. 29,416) from the previous one (i.e. 1,879,986) we get 1,850,570. (7) This is the required ahargaṇa. Since division by 7 leaves