When did Austria-Hungary declare war on Serbia?

Austria-Hungary declared war on Serbia on July 28, 1914.1234

Following the assassination of Archduke Franz Ferdinand on June 28, 1914, the Austro-Hungarian government, led by Foreign Minister Leopold, Count von Berchtold, sought to use the event to settle its conflict with Serbia. After issuing a deliberately provocative ultimatum on July 23, which Serbia largely accepted but rejected on two points involving national sovereignty, Austria-Hungary severed diplomatic relations. On July 28, Berchtold persuaded Franz Joseph to sign the declaration of war, aiming to establish a fait accompli before other European powers could intervene.124