Does the separation date affect alimony in your state? I know that it took two years for my ex and I to finalize our divorce after he moved out - but the length of the marriage for alimony purposes was based on the separation date. I think you can effectively argue that date. Otherwise if you live in a state where you have to be separated for a year before you can finalize the divorce, you may not want to debate that point as it would keep you tied to him too. Good thing to discuss with your lawyer.
