1640 followed by 1641
1640 (MDCXL) was a leap year starting on Sunday of the Gregorian calendar and a leap year starting on Wednesday of the Julian calendar, the 1640th year of the Common Era (CE) and Anno Domini (AD) designations, the 640th  year of the 2nd millennium, the 40th  year of the 17th century, and the  1st   year of the 1640s decade. As of the start of 1640, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.