Acts Interpretation Act 1901

In any Act, month means a period:

starting at the start of any day of one of the calendar months; and

ending:

immediately before the start of the corresponding day of the next calendar month; or

if there is no such day—at the end of the next calendar month.

A month starting on 15 December in a year ends immediately before 15 January in the next year.

A month starting on 31 August in a year ends at the end of September in that year (because September is the calendar month coming after August and does not have 31 days).

In any Act, a reference to a period of 2 or more months is a reference to a period:

starting at the start of a day of one of the calendar months (the starting month); and

ending:

immediately before the start of the corresponding day of the calendar month that is that number of calendar months after the starting month; or

if there is no such day—at the end of the calendar month that is that number of calendar months after the starting month.

A reference to 6 months starting on 15 December in a year is a reference to a period starting on that day and ending immediately before 15 June in the next year.

A reference to 6 months starting on 31 October in a year is a reference to a period starting on that day and ending at the end of April in the next year (because April is the calendar month coming sixth after October and does not have 31 days).