Question: When did construction start on the sydney harbour bridge?
Answer: 28 July 1923
Disambiguated questions and answers: question: When did construction officially start on the sydney harbour bridge?
When did construction of the Arch start on the sydney harbour bridge?
answer: 28 July 1923
26 October 1928
Natural Questions answer: on 28 July 1923 (from the Wikipedia article "Sydney Harbour Bridge")