To understand sanskrit words is highly critical when it poise polysemous nature. A wrong conjecture in Astronomical sense can shift the epochs by drastic time gap which requires a speacial attention and gathering of textual evidence as much as possible.
Identifying Udagayana-Praśna 1, Section 1; अथ कर्माण्याचाराद्यानि गृह्यन्ते १; 1. Now (follow) the ceremonies (the knowledge of) which is derived from practice (and not from the Śruti). 2. उदगयनपूर्वपक्षाहःपुण्याहेषु कार्याणि २; They should be performed during the northern course of the sun, on days of the first fortnight (of the month), on auspicious days,
Praśna 1, Section 2; सर्वऋतवो विवाहस्य शैशिरौ मासौ परिहाप्योत्तमं च नैदाघम् १२; 12. All seasons are fit for marriage with the exception of the two months of the śiśira season, and of the last summer month.
Praśna 1, Section 2; 16. Under the Invakās (Nakṣatra), (the wooers who go to the girl’s father) are sent out: such wooers are welcome. footnote>On the Nakṣatra Invakās, comp. Section 3, Sūtra 4. This Sūtra forms a Śloka-hemistich, on which Haradatta observes, ‘This verse has not been made by the Sūtrakāra.'< Such editing, addition and alterations happen due to change in season and precession of equinoxes which points to different Nakshatra at different epoch.
The above reading clears all the doubt on the word “Udagayana”. For the the auspicious ceremonies, like marriage, has to begin in Udagayana but with an exception of the śiśira season.
The above reading clears all the doubts on the word “Udagayana”. For the auspicious ceremonies, like marriage, has to begin in Udagayana but with an exception of the śiśira season. If Northern course Udagayana has to be from Wintersolstice in Āpastamba-gṛhya-sūtra then the exception of the śiśira season should not have been mentioned neither this would corroborate “northern course of the sun, on days of the first fortnight (of the month), on auspicious days,”, i.e., it would not have mentioned the first fortnight after śiśira since śiśira begins with winter solstice, which is prohibited. The two statements become contradictory. We have a long tradition of reading about marriages, copulation, Rati-Kāmadeva Mahotsava in the Vasanta season in Indic texts and poetries.
The takeaway of this study
Thus, if Northern course, i.e., Udagayana has to be from Wintersolstice in Āpastamba-gṛhya-sūtra then the exception of the śiśira season should not have been mentioned.
This also clears the fog from the words like Udagayana and Uttarāyana. Udagayana means Sun in “Northern Hemisphere” and not “the northern course of the sun”. The northern course of the sun is clearly stated as Uttarāyana in Jyotiṣa texts like Sūryasiddhānta. Sūryasiddhānta has differentiated between Deva-Ayana/Devayāna and Uttarāyana. All the Indic texts compliment each other.
This study will have implications on dating of Vedāṅga Jyotiṣa.