Queen Elizabeth II was born on 21 April 1926 at 2.40 AM to the Duke (later King George VI) and the Duchess of York at 17 Bruton Street, London – the home of the Duchess of York’s parents. She was given the names Elizabeth Alexandra Mary, after the Duchess of York (Queen Elizabeth the Queen Mother now deceased).
https://www.statusquo.org/aru_html/html/birthday.html
With the exception of Western Australia and Queensland, the Queen’s birthday was celebrated in Australia on Monday, 12 June 2017
