Which park?
I remember it was 2pm for me (also Queensland) to fasspasses which also opens at midnight for WDW. Disneyland can open ADRs between midnight to 6am Disney time but you don't have to be there when it switches over so I just plan to give a casual check when my 60 days out window opens.
Best way I found for myself to keep track of the time difference was to use my clock app on my iPhone (sorry no tips if you don't have one) and have the two time zones side by side rather than trying to calculate it in my head.
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