1618 (MDCXVIII) was a common year starting on Monday of the Gregorian calendar and a common year starting on Thursday of the Julian calendar, the 1618th year of the Common Era (CE) and Anno Domini (AD) designations, the 618th year of the 2nd millennium, the 18th year of the 17th century, and the 9th year of the 1610s decade. As of the start of 1618, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.