diamond jubilee
From Longman Dictionary of Contemporary EnglishRelated topics: Chronologydiamond jubileeˌdiamond ˈjubilee noun [countable] TMCthe date that is exactly 60 years after the date of an important event, especially of someone becoming a king or queen → golden jubilee, silver jubileeExamples from the Corpusdiamond jubilee• In 1968, the diamond Jubilee came and went without celebration for fear of a financial loss!