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
Buddhist calendar the Buddhist Era (as the Buddhist calendar straddles the Gregorian calendar—currently from April to April). In Sri Lanka, the difference between BE and CE is 544. The calendar recognizes two types of months: synodic month and sidereal month. The Synodic months are used to compose the years while the 27 lunar sidereal days (Sanskrit: "nakshatra"), alongside the 12 signs of the zodiac, are used for astrological calculations. (The Burmese calendar also recognizes a solar month called "Thuriya Matha", which is defined as 1/12th of a year. But the solar month varies by the type of year such as tropical year,