This often happens in soial security and tax legislation. So you get different versions, when looking onto the norm before or after the retroactive enactment was published.
This was considered in the legal database of austrian social securities http://www.sozdok.at/.
You can find some explanation in the section „Fragen“ – look for „Zeitschichtenaufbereitung, Sicht- und Stichtag“.
Filed under: legal information, consolidation, time layers