Abstract The frst theoretical system of tracking sun in the tropical annual cycle is cryptically mentioned in the Maitrāyaṇīya Āraṇyaka Upaniat (MAU) of the Kṇa Yajurveda, as the southern sojourn of sun starting at the summer solstice. This is called maghādyaṁ, the frst point of the maghā nakatra, identifed most likely with the early morning visibility of ε-Leo, near the azimuth of the sunrise point on the horizon as observed at Kurukshetra. Twenty seven equal nakatra sectors named in the traditional sequential order cover one tropical circuit of sun of 366 days with the winter solstice falling exactly at the middle of the śravihā sector. Even though MAU mentions each nakatra to be made up of four quarters, no practical application of this ¼-nakatra sky part amounting to 3º20´ in longitude is seen in Vedic texts till we come to the Brahmāṇḍa Purāṇa, a text closer to the Vedas. This Purāṇa states, observed equinoctial full moon positions corresponding to spring equinox at ¼-kttikā and autumn equinox at ¾-viśākha exactly 180º apart as they should be. This statement is analysed in this paper by computer simulation of full moon time series for the years − 2400 to − 800 to show that the Purāṇa data would be real- istically valid for the period 1980 BCE to 1610 BCE. It is further demonstrated that the Purāṇa has followed the maghādi system of solar nakatra system stated in the MAU. The central epoch circa 1800 BCE of this maghādi equal nakatra solar zodiac got modifed, due to precession efects, to the śravihādi scheme of Parāśara, Vṛddha Garga and Lagadha dateable to circa 1300 BCE. Keywords Brahmāṇḍa Purāṇa · Maghādi solar zodiac · Equinoctial full moon · Epoch 1800 BCE · Precession efects
