1606 (MDCVI) was a common year starting on Sunday of the Gregorian calendar and a common year starting on Wednesday of the Julian calendar, the 1606th year of the Common Era (CE) and Anno Domini (AD) designations, the 606th year of the 2nd millennium, the 6th year of the 17th century, and the 7th year of the 1600s decade. As of the start of 1606, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.