1667 (MDCLXVII) was a common year starting on Saturday of the Gregorian calendar and a common year starting on Tuesday of the Julian calendar, the 1667th year of the Common Era (CE) and Anno Domini (AD) designations, the 667th year of the 2nd millennium, the 67th year of the 17th century, and the 8th year of the 1660s decade. As of the start of 1667, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.