This is a standard way of saying this in legal documents and statutes

From a certain date henceforward/henceforth (legalese style).

Found in Babylon:

d'ora in avanti, per l'avvenire {henceforth}
d'ora in avanti {henceforward}

With the Italian translation

From a certain date onwards

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Note added at 1 hr (2010-06-29 13:08:36 GMT)
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See for example:
http://www.hse.gov.uk/mining/legislatlist.htm
The Office of Public Sector Information (OPSI) link to external website[4] provides the full as made text of Acts from 1988 onwards and Regulations from 1987 onwards as they were enacted and these can be downloaded free of charge.
http://www.opsi.gov.uk/legislation/scotland/s-act-si
This page provides links to the full text of all UK Acts of Parliament and Statutory Instruments (from 1988 onwards) and any accompanying Explanatory Notes and Explanatory Memoranda...
http://portal-live.solent.ac.uk/library/subject_guides/law/u...
These can be used to check all amendments, modifications, repeals etc to all primary (Acts) and secondary (Statutory Instruments). Current Law Legislation Citators| cover the period from 1947 onwards.

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Note added at 1 hr (2010-06-29 13:22:01 GMT)
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http://www.nationalarchives.ie/topics/Nat_Schools/natschs.ht...
Only one model school was first contemplated, a central model school in Dublin which was established in 1833. From 1845 onwards, local model schools began to be established; managed by the local inspectors, their teachers were directly appointed by the Board.
http://churches-of-christ.ws/early.htm
When the Roman Emperor Constantine the Great legalised Christianity from 313 onwards the church became popular with the pagan masses.
http://www.policecaruk.com/ClassicFleet/files/MorrisMinorART...
Production of the Minor gradually ceased from 1969 onwards;

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Note added at 1 hr (2010-06-29 13:25:57 GMT)
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http://www.orbitalsound.co.uk/index.htm?contentframe=http://...
LABOUR CONDITIONS OF FREELANCE EMPLOYMENT FROM 2005 ONWARDS