When did God reckon our old Adam crucified with Christ?
At the moment of belief, God in His omnipotence and sovereignty reckoned the old Adam as crucified with Christ. This is a positional reckoning: the old nature is dead, yet in experience it remains present, plaguing the believer until leaving this mortal body.
Les teaches that Paul in Romans 6 deals with reckoning the old Adam as our mortal enemy and putting him constantly to death. The moment a person believes, God in His omnipotence and sovereignty reckoned that old Adam as crucified with Christ, so he is dead positionally. Yet in experience the old nature remains, plaguing the believer until leaving this body of mortality. This is part of the Pauline doctrine of two natures: the old sin nature warring against the new divine nature.