Anzac Day is a national day of remembrance in Australia and New Zealand
that broadly commemorates all Australians and New Zealanders "who
served and died in all wars, conflicts, and peacekeeping operations" and
"the contribution and suffering of all those who have served." Observed on 25 April each year, Anzac Day was originally to honour the members of the Australian and New Zealand Army Corps (ANZAC) who fought at Gallipoli against the Ottoman Empire during World War I.
Anzac Day is also observed in the Cook Islands, Niue, Pitcairn Islands, and Tonga, and previously also as a national holiday in Papua New Guinea and Samoa. Wikipedia