This is a debated topic in the BaZi community. Traditional BaZi was developed in the Northern Hemisphere and ties elements to seasons (summer = Fire, winter = Water).
In the Southern Hemisphere, seasons are inverted. A person born in July in Australia experiences winter, not summer. Some practitioners argue the chart should be adjusted to reflect the local seasonal qi. Others maintain that the solar calendar's elemental assignments are astronomically fixed and apply globally.
The majority view among modern international practitioners: use the standard calculation without seasonal inversion, but interpret with awareness of local conditions. A Fire Day Master born in an Australian winter is still a Fire Day Master — but their experience of that Fire may differ from a Northern Hemisphere counterpart. The chart works; the interpretation adapts.
When in doubt, test your chart against your actual life experience. The accurate interpretation is the one that resonates.