The Orion, or Researches into the Antiquity of the Vedas c6.54.1

c6.54.1

In the absence of anything to the contrary we might therefore take it as established that in the early Vedic days the year began when the sun was in the vernal equinox; and as the sun then passed from the south to the north of the equator it was also the commencement of his northern passage. In other words, the Uttarāyaṇa (if such a word was then used), Vasanta, the year and the Satras all commenced together at the vernal equinox. The autumnal equinox which came after the rains was the central day of the year; and the latter half of the year was named the Pitṛyāṇa or what we would now call the Dakṣiṇāyana. It is difficult to definitely ascertain the time when the commencement of the year was changed from the vernal equinox to the winter solstice. But the change must have been introduced long before the vernal equinox was in the Kṛttikās, and when this change was made uttarāyaṇa must have gradually come to denote the first half of the new year, i. e., the period from the winter to the summer solstice, especially as the word itself was capable of being understood in the sense of "turning towards the north from the southernmost point," I am of opinion, however, that devayāna and pitṛyāna, or devaloka and pitṛloka were the only terms used in the oldest times. It is a natural inference from the fact that the word uttarāyaṇa, as such, does not occur in the Rigveda.