If I know apparent planetary positions how do I calculate the date? I have planetary position in retrograde  how do I calculate the date?
For eg, I know Mars was in retrograde in Scorpion (Sidereal 210 to 240 deg), how do I calculate the date and year of this?
As of now the only other info I have is that just days before this was a lunar eclipse where Sun was in Libra.
Just a year or two before this
Mars was in retrograde in first half of Leo and at this time Jupiter was placed at Capricorn. These are all sidereal observations.
P.S: This is regarding an ancient scripture citation where it was said Mars was in retrograde in Scorpion, current proposed dates range from 500 BC to 6000 BC. This is all the information I have, that Mars was is in retrograde in sidereal scorpion and I want to find possible date of this happening. The iterative approach would take too long, because the span is about thousands of years
Mars's ~72 day retrograde loop occurs every ~2.1 years and intersects a given constellation once or twice every 15 or 17 years.
The more information you have about the positions of other planets, e.g. Jupiter or Saturn, the more you can narrow the set of possible dates.