Āryabhaṭa I’s astronomy with midnight day-reckoning

Abstract

Āryabhaṭa I (born 476 AD) is generally known as the author of the Āryabhaṭīya and his fame as a mathematician and astronomer of the first rank is assessed on the basis of that work alone. No other work written by him is available to us. But there are reasons to believe that he was the author of at least one more work on astronomy. References to two works of Āryabhaṭa I, one in which the day was reckoned from sunrise (and is known as Āryabhaṭīya) and the other in which the day was reckoned from midnight, have been made by posterior Hindu astronomers.