The Orion, or Researches into the Antiquity of the Vedas c6.54.2

c6.54.2

The fact, that Viṣuvān was the central day of the yearly satra, further shows that the sacrificial system was coeval with the division of the year into the paths of Devas and Pitṛs. After a certain period the beginning of the year was changed to the winter solstice, and it was sometime after this change was made that the words uttarāyaṇa and dakṣiṇāyana came to be used to denote the solstitial divisions of the year. But devayāna and pitṛyāna could not be at once divested of the ideas which had already become associated with them. Thus while new feasts and sacrifices came to be regulated according to uttarāyaṇa and dakṣiṇāyana, devayāna and pitṛyāna with all the associated ideas continued to exist by the side of the new system, until they became either gradually assimilated with the new system or the priests reconciled the new and the old systems by allowing option to individuals to follow whichever they deemed best. We must therefore take great care not to allow the idea of *uttarâyaṇa*, as we now understand it, to obscure our vision in interpreting the early Vedic traditions, and that too much care can never be taken is evident from the fact that even so acute an astronomer as Bhâskarâchârya was at a loss to correctly understand the tradition that the Uttarâyaṇa was the day of the Devas. In his Siddhânta Shiromaṇi he raises the question how the Uttarâyaṇa, as it was generally understood in his day, could be the day of the Devas.