Proleptic Gregorian calendar Proleptic Gregorian calendar The proleptic Gregorian calendar is produced by extending the Gregorian calendar backward to dates preceding its official introduction in 1582. In countries that adopted the Gregorian calendar later, dates occurring in the interim (between 1582 and the local adoption) are sometimes "Gregorianized" as well. For example, George Washington was born on February 11, 1731 (Old Style), as Great Britain and its possessions were using the Julian calendar with English years starting on March 25 until September 1752. After the switch, that day became February 22, 1732, which is the date commonly given as Washington's birthday. The proleptic
Adoption of the Gregorian calendar Gregorian year 2019 corresponds to Heisei 31. Korea started using the Gregorian calendar on 1 January 1896, which was the 17th day of the 11th lunar month not only in Korea but also in China, which still used the lunisolar calendar. The lunisolar Korean calendar is now used for very limited unofficial purposes only. The North Korean calendar uses Gregorian months and days, but with Kim Il-Sung's year of birth (1912) used as year 1. The Republic of China government under Provisional President Sun Yat-sen abolished the lunisolar Chinese calendar and adopted the Gregorian calendar on 1 January 1912. The