Seperation Date

My Spouse left a house in Aug of 08 and he is telling me which this is a date of seperation even though he didn't record for divorce until May of 09.  He didn't do this deliberately which I can tell, but it is an area of contention right away and do I have any real grounds for fighting this in court.  My arrogance is which we went to 2 or 3 marriage couseling event in a fall of 09 so I would reason which a time upon a 2 year duration in PA would start in December of 08 and not Aug of 08