golden jubilee
From Longman Dictionary of Contemporary Englishgolden jubileeˌgolden ˈjubilee noun [countable] British English CELEBRATEthe date that is exactly 50 years after an important event, such as the occasion when someone became king or queen SYN golden anniversary American English → diamond jubilee, silver jubilee the Queen’s golden jubilee celebrationsExamples from the Corpusgolden jubilee• The highlight of Gibson's later years was the Polyethylenes 1933-83 golden jubilee conference in London in June 1983.