golden anniversary
From Longman Dictionary of Contemporary Englishgolden anniversaryˌgolden anniˈversary noun (plural golden anniversaries) [countable] especially American EnglishCELEBRATE the date that is exactly 50 years after the beginning of something, especially a wedding SYN golden wedding, golden jubilee British English → diamond anniversary, silver anniversaryExamples from the Corpusgolden anniversary• Success is also particularly appropriate this year, as the band is celebrating its golden anniversary.