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 government in 1912 as the start rather than the regnal year of an emperor. The adopted calendar in both mainland China and Taiwan are called the "Public Calendar" (), or "New Calendar" (). Months in Gregorian calendar in Chinese are rarely named, instead they are usually numbered. For instance, Gregorian calendar December in China are usually written as month 12. On the other hand, in Chinese calendar, the 11th month and 12th month are usually nicknamed. Orally, people are accustomed to call the date in the month as "No. "dd"", for example, the Spring Festival of this year (2017) is