1920 followed by 1921
1920 (MCMXX) was a leap year starting on Thursday of the Gregorian calendar and a leap year starting on Wednesday of the Julian calendar, the 1920th year of the Common Era (CE) and Anno Domini (AD) designations, the 920th  year of the 2nd millennium, the 20th  year of the 20th century, and the  1st   year of the 1920s decade. As of the start of 1920, the Gregorian calendar was 13 days ahead of the Julian calendar, which remained in localized use until 1923.