1720 followed by 1721
1720 (MDCCXX) was a leap year starting on Monday of the Gregorian calendar and a leap year starting on Friday of the Julian calendar, the 1720th year of the Common Era (CE) and Anno Domini (AD) designations, the 720th  year of the 2nd millennium, the 20th  year of the 18th century, and the  1st   year of the 1720s decade. As of the start of 1720, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.