Doubt about weekly Navigo pass

Hi all.

I will be arriving in Paris tonight around 22.30 at CDG airport, so i will probably be getting a train from CDG to the centre. I was planning on buying a weekly pass (31.60). I know its validity is monday-sunday. Can I wait for midnight to get the RER to the city and have the fare included in the weekly pass? Would that work or does it only count from the morning after?