Q:Given the following passage  "On June 22, 1990, Volodymyr Ivashko withdrew his candidacy for leader of the Communist Party of Ukraine in view of his new position in parliament. Stanislav Hurenko was elected first secretary of the CPU. On July 11, Ivashko resigned from his post as chairman of the Ukrainian Parliament after he was elected deputy general secretary of the Communist Party of the Soviet Union. The Parliament accepted the resignation a week later, on July 18. On July 16 Parliament overwhelmingly approved the Declaration on State Sovereignty of Ukraine - with a vote of 355 in favour and four against. The people's deputies voted 339 to 5 to proclaim July 16 a Ukrainian national holiday.",  answer the following question. Note that the answer is present within the text.  Question: when did Ivashko's resignation become official
A:
July 18