Please refer also to this post on the data of varahamihira for the saka year discussion : https://ancientindians.in/2010/01/01/varahamihira-really-427-of-saka-era-pancha-siddhantika/
Reference : Please see the Image below from the book : Vedanga Jyotisha of Lagadha: Prof. T.S. Kuppanna Sastry : Introduction: Pg 13.
- This page says that Varahamihira said that the winter solstice was in 1st pAda of uttarASADa nakSatram.
- Today, we take it that, the point marked by the winter solstice is the (middle of the) mUla nakSatram.
- Beginning of mUla 1st to end of uttarASADa 1st is 30 degrees, or a precession of equinoxes of approximately 2000 years. (30*71.6 = 2148 years)
- mUla mid to beginning of uttarASADa first, will give us 1432 (20*71.6) years, approximately. The solstice lasts in each pAda of a nakSatram for about 239 years. So using nakSatra pAdA: for dating cannot give us a better accuracy than this.
- So varAhamihira’s date can be between 132 BCE to 584 CE. (2016-2148, 2016-1432)
- *Subject to verification of the ślOkam referred to below.