Forgive me if this is posted in the wrong place of the forum.
In doing research on Saturn Returns around the internet, I came across this site that has a Saturn Return Calculator.
It *seems* as though it works correctly. I entered my own birthdate and it accurately calculated my first Saturn return (start and end date, as well as other Saturn related information).
I do not own, nor am I affiliated with this site or it's content in anyway, I just preformed a web search with the key terms " how to calculate a saturn return" and this is what popped up.
I looked around the forum and it looks as though this hasn't been mentioned, so I thought it might be be helpful to others.
Here is the link: http://www.astrocal.co.uk/saturn-return.htm