सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

10 mean sidereal revolution takes roughly 11.8 years, five revolutions take 59 mean solar years. The sixtieth year thereafter of the Jovian Cycle is considered as an Adhi- Samvatsara thereof so that the luni-Solar reckoning as well as the jovian reckoning get wedded together. Thus to get the jovian year we have simply to add 27 to the luni, solar year. The wedding of the two reckonings has its analogy in the process of intercalation which weds the solar reckon- ing with the luni-Solar only with the difference that months of the latter reckoning are set apart as Adhika or extra months. Just as the process of intercalation brings in its train what is called a Kshayamāsa as per the convention that, that month would be set apart as an Adhikamāsa, which does not carry a Samkrānti ie entrance of the Sun into the next Rasi, in which process there appears a month in which there may occur two Samkrāntis which is hence considered as a Kshayamāsa, just in a similar way that luni-Solar year in which the Jupiter enters the next Rasi, is supposed to be normal whereas that year in which such an entrance does not take place is deemed an Ādhika year and set apart while that year which carries two entrances is deemed as a Kshya year. The pro- cess of intercalation which weds together the solar and the luni-solar reckonings will be elucidated further in its appro- priate context. The word Sāmhitikas means the authors of the works called Samhitas like the Varāha-Brihatsamhita etc. Verse 31. The manushya-māna or that which men follow, adopts the year, the Ayana the Ṛtu or the season (six in number during an year) and the yuga according to the movement of the Sun ie according to Sauramāna the months and the thithis according to the luni-solar reckon- ing ie according to Chāndramāna the Vratas, upavāsas, treatment of diseases, deliveries of ladies, the names of the weeks all these according to the reckoning of civil days ie according to Sāvanamāna and finally the ghatis Vighatis etc. etc. according to the Nākshatramāna.