Formula for calculating an Ephemeris table

Here's an obscure question:

I need to be able to determine historical astrolo开发者_如何学Cgical periods (semi) accurately. I am looking for a way to calculate the start and end dates of a given zodiac sign period given a geographical coordinate and a year.

The purpose of the algorithm is to determine the possible dates of birth for a person whose astrological sign, year and place of birth is known for the Open Ancestry project. I will convert the implementation to C#.

Does anyone know of a semi reliable source for an existing Ephemeris table or a way to create one programmatically? I really just need a start point so it doesn't matter if the geographical parts of the formula or table are missing as long as the mechanism for approximating the start and end (given a specific year) are shown.

The programming language for an algorithmic approach is not important.

Why don't you look at the source of stellarium (was able to go quite far in the past)? I am sure the whole thing is an overkill for you, but maybe you can dig up their resources or contact somebody involved with it?