Hayanaratna · by Balabhadra
Chapter 1 · Planets, Signs, Year Entry
ग्रहराशिस्वरूपवर्षप्रवेशाद्यानयनाधिकारः
अथवा ॥ अधिमाससंभवे त्रयोदशमासानां सत्त्वात्पूर्वोक्तं सूर्यसिद्धांतवचो लोकप्रसिद्धं च व्याहन्येत ॥ तस्मात्सौरमानेनैव मासदिनप्रवेशादिकं विधेयमितिसिद्धांतः ॥
Or else: with an adhimasa (extra lunar month), there would be thirteen months. Then the Surya Siddhanta's words given before, and common use, would be broken. So the settled view is this. The entry of the month, the day and the rest is made by solar measure only.
Simple meaning: Solar months: an extra lunar month would make thirteen months in a year, so months and days are solar.
अथ वर्षप्रवेशसमये स्वस्वाधीतसिद्धांतकरणादिरीत्या साधितोर्कौ जन्मकालीनार्केणावश्यं समो भवति ॥ इदमेव वर्षप्रवेशसमये प्रमाणम् ॥
Test of the year entry: the Sun found by one's own method must equal the birth Sun.
उक्तंच समरसिंहेन ॥
Samarasimha: the true Sun at the year entry stands where it stood at birth.
श्रीमन्नीलकंठज्योतिर्विंद्भिरप्युक्तम् ॥
Nilakantha: at the year entry the Sun equals the birth Sun.