tmpffisch - I think I can help ... Is a good question!
Documents and charts issued in accordance with the AIRAC cycle
become effective at 1600 hours UTC on the day prior to the
nominated date unless otherwise notified; eg, a document with an
AIRAC date 26 Jun becomes effective 06251600UTC (ie, during
Australian Eastern Standhours local on 26 Jun).
AIP GEN 4.3