From the WIA, original post here.

Date : 15 / 01 / 2016 
Author : Jim Linton – VK3PC

The Australian Communications and Media Authority (ACMA) automatically allows all radio amateurs to substitute their normal VK callsign prefix with the letters AX, every Australia Day.  Our national day this year falls on Tuesday January 26.  This gives radio amateurs the chance to be part of the commemoration the First Fleet’s arrival in 1788 at Sydney Gove and the establishment of a European settlement at Port Jackson, with the raising of the British flag by Governor Arthur Phillip.

On Australia Day many celebrate our country and culture.  This includes the granting of awards, honours and the welcoming to citizenship of many immigrants.  National flags will be flown and the celebrations include fireworks displays.

The AX prefix is popular among prefix hunters and others.  The use of a special QSL card is encouraged by the Wireless Institute of Australia.  The same alternative AX prefix applies on ANZAC Day, April 25 and International Telecommunications Day, May 17.