A Work by the Illustrious Brahmagupta

...5;17;52;16. Subtracting this, the midnight mean Moon, like the one previously calculated, is 5;17;37;31. According to the intention of the arya verse, this is not [calculated] by Brahmagupta. Therefore, the Moon obtained from the day-count in this sequence is because it is established by the principle of finding the Moon and Sun. Since the Sun, which is the mean Moon minus the correction derived from the remainder of lost lunar days multiplied by 3, is obtained, it has not been explained. Now, he describes the finding of the Sun and Moon from the day-count in two arya verses:

Divided by 696, the remainder of the lost lunar days is added to the day-count. Also, from the remainder of the intercalary months multiplied by 20 and divided by 610... original: "dinavarasabhaktamavāvaśeṣamāptadināditatsahitāt. adhimāsaśeṣakācca vimśadguṇitāttukhadigbhiḥ" ||1||
The sum of the month and day is separately multiplied by 13 and decreased by the second [value]. Thus, two mean signs of the Sun and Moon are [obtained]. original: "māsadinaprathamaikyam prthak trayodaśaguṇam dvitīyonam. dvāpyevam madhyau rāśyāvārkacandrau vā" ||2||

Meaning of the verse: "Dinavarasabhaktam" means 2, 9, and 6 the number 692. Divided by those is "Dinavarasabhaktam". What is that? He says: "Avamaseṣam" remainder of lost lunar days. "Avamadinadau" means the remainder of lost lunar days and the days, etc. "Tatsahitam" means added to that. From what? From the remainder of the intercalary months. "Vimśadguṇitāt" means multiplied by 20. "Dinavarairavamaseṣādāmena" means having made the remainder of the intercalary months greater by the days, etc., of the lost lunar days, multiply by 20. From that, "Rtukhadigbhih" means the seasons, zero, and the directions 6, 0, 10, i.e., 1006. That is the meaning. "Masadinaprathamaikyam" means the sum of the months and days is the first. Starting from the bright fortnight of Chaitra, the months and days given in the day-count are to be made into days by the remainder of the lost lunar days. "Prthak trayodaśaguṇam" means separately in the second place. Multiplied by 13 is "Trayodaśaguṇam". The sum of the months and days in the second place should be multiplied by 13. In such a way, the signs are then decreased by the second [value]. "Dvapyevamvidhau" means two such. "Rashyadyau" means signs at the beginning. "Arkadandrau" means the Sun and Moon. The word "ca" and here is for the type.