Aryabhatiya, an improved work, is product of mature intellect , which he wrote when he was 23 years old. Unlike in the Aryabhata siddhanta , the civil days are reckoned from one sunrise to the next, a practice which is still prevalent among the followers of Hindu calendar.
... it is extremely likely that Aryabhata knew the sign for zero and the numerals of the place value system. This supposition is based on the following two facts: first, the invention of his alphabetical counting system would have been impossible without zero or the place-value system; secondly, he carries out calculations on square and cubic roots which are impossible if the numbers in question are not written according to the place-value system and zero.
He mentions his name at three places only as “Aryabhata”, towards the beginning and ending Verses of his work Aryabha?ya,
The second reason adduced, viz., that Aryabhata should have hailed from Kerala is fragile. Besides the Aryabhatan system being prevalent in this land,-“all” commentaries on Aryabha?ya have been produced by Kerala astronomers really does not stand scrutiny.
His fame rests mainly on his Aryabhatiya, but from the writings of Varahamihira (Sixth century AD), Bhaskara I, and Brahmagupta (seventh century) it is clear that earlier he composed the Aryabhata Siddhantha (voluminous) is not extant. It is also called Ardharatrika Siddhanta , because in it the civil days were reckoned from one midnight to the next; 34 verses on astronomical instruments from this have been quoted by Ramakrishna Aradya.
He was the father of the Indian cyclic astronomy which resulted in the planetary theory that determines more accurately the true positions and distances of the planets (including the Sun and the Moon )...was also the first to produce celestial latitudes...proposed the scientific cause of eclipses as against the mythological demon Rahu [Moon's node]. His ideas resulted in the new school of Indian Astronomy – the Aryapasha ((Aryabhata School) based on the text of Aryabhatiya.