Australien: Winterzeit

The correct German article for is "die" (feminine).

So it is: (Though more natural in German: die Winterzeit in Australien ) australien winterzeit

If you meant the country alone: das Australien (neuter, because country names with -ien are neuter: das Australien – though usually used without an article). The correct German article for is "die" (feminine)

australien winterzeit australien winterzeit