Tomorrow, 26th of January, is a holiday here in Australia - Australia Day.
If you are curious how to say it in Chinese, that would be 澳大利亚国庆节 (àodàlìyà guóqìngjié). And you can say: 澳大利亚国庆节快乐! (àodàlìyà guóqìngjié kuàilè), where 澳大利亚 (àodàlìyà) is Australia, 国庆节 (guóqìngjié ) is "national holiday" and 快乐 (kuàilè) is "merry", so the meaning of this phrase is "Happy Australia Day!"
In 1788 the First Fleet of British ships arrived at Port Jackson, New South Wales, and the flag of Great Britain was raised at Sydney Cove. Nowadays people celebrate the anniversary with various community events. Tomorrow I am going to watch the parade!