Dr. A.Krishna Upadhyay, IPS, (9437034172, firstname.lastname@example.org)
According to Varahamihir himself , he was born on Chaitra Shukla 8, yudhishthira Shaka 3042 i.e 6-3-95 AD. He was one of the 9 Ratnas in the court of Vikramaditya parampara King of Ujjain (82 BC – 19 AD), who started Vikramna Samvat in 57 BC. Varahamihir died at the age of 90 in 5 BC. How can his “shaka” mean Shalivahana Shaka, which started in 78 AD, i.e 83 years after his death.
Brahmagupta was famous as son of Jishnugupta, contemporary of Varahamihir. As per Brihat – Jataka, chapter 8, Jishnugupta was the son of the famous king of Nepal, Avanti Varman (103 – 33 BC), in whose time Vikramaditya started Vikrama era in 57 B.C. Time of Brahmagupta also is in Sir Harsha Shaka of 456 BC, not in 78 AD Shaka which started after his death.
Vedanga jyotish takes the start of an year from Dhanishta Nakshatra. This started with Karthikeya in 15 800 BC, when pole shifted from Abhijit (Mahabharata, Vana Parva (230) 8-10). It did not start after Mahabharata. Then, Parashara and Aryabhata were contemporary as per Mahasiddhanta (2/2) of Aryabhata – 2.
Aryabhata 1 was in 360 Kali, when his calculations fit. This has been changed to 3600 Kali by G. Thibant., when it doesn’t make sense