1680 (MDCLXXX) was a leap year starting on Monday of the Gregorian calendar and a leap year starting on Thursday of the Julian calendar, the 1680th year of the Common Era (CE) and Anno Domini (AD) designations, the 680th year of the 2nd millennium, the 80th year of the 17th century, and the 1st year of the 1680s decade. As of the start of 1680, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.
