Anzac Day is on the 25th of April, it commemorates all of the New Zealand's men who died in the war and honours returned servicemen and women. ANZAC stands for Australian New Zealand Army Corps.
The date itself marks the anniversary of the landing of New Zealand and Australian soldiers (The Anzacs) at Gallipoli surrounded with water in 1915. The aim was to capture the Dardanelles, the gateway to the Bosphorus and the Black Sea. At the end of the fight, Gallipoli was still held by its Turkish defenders.
Thousands lost their lives in the Gallipoli campaign: 87,000 Turks, 44,000 people from France and the British Empire, including 8500 Australians. To this day, Australia also marks the events of 25 April. Among the dead were 2779 New Zealanders, about a sixth of those who served on Gallipoli. That's a lot of dead people!