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. It has been defined in the international standard ISO 8601.

Most Maya scholars use the Gregorian calendar, especially when converting Long Count dates (first century BC to tenth century). It is also explicitly required for all dates before 1582 by ISO 8601:2004 (4.3.2.1), if the partners to information exchange agree. However, neither astronomers nor non-Maya historians generally use it.

For these calendars we can distinguish two systems of numbering years BC. Bede and later historians did not use the Latin zero, "nulla", as a year, so the year preceding AD 1 is 1 BC. In this system the year 1 BC is a leap year (likewise in the proleptic Julian calendar). Mathematically, it is more convenient to include a year zero and represent earlier years as negative, for the specific purpose of facilitating the calculation of leap years BC. This is the convention used in astronomical year numbering and in the international standard date system, ISO 8601. In these systems, the year 0 is a leap year.

Note that the Julian calendar was in actual use from 45 BC until 1582 or later (see From Julian to Gregorian), so historians and astronomers prefer to use the actual Julian calendar during that period. Likewise, the proleptic Julian calendar is used to specify dates before AD 1, the first common year that did not follow a quadrennial leap year (leap years between 45 BC and 1 BC were irregular, see Leap year error). But when seasonal dates are important, the proleptic Gregorian calendar is sometimes used, especially when discussing cultures that did not use the Julian calendar.

The proleptic Gregorian calendar is sometimes used in computer software to simplify the handling of older dates. For example, it is the calendar used by MySQL [http://dev.mysql.com/doc/refman/5.0/en/mysql-calendar.html] and by CIM.

Difference between Julian and proleptic Gregorian calendar dates

Before the introduction of the Gregorian calendar, the difference between Julian and proleptic Gregorian calendar dates were as follows:


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Proleptic Julian calendar — The proleptic Julian calendar is produced by extending the Julian calendar to dates preceding AD 4 when its quadrennial leap year stabilized. The leap years actually observed between its official implementation in 45 BC and AD 4 were erratic, see …   Wikipedia

  • Gregorian calendar — For the calendar of religious holidays and periods, see Liturgical year. For this year s Gregorian calendar, see Common year starting on Saturday. 2011 in other calendars Gregorian calendar 2011 MMXI …   Wikipedia

  • Proleptic calendar — may refer to:* Proleptic Gregorian calendar * Proleptic Julian calendar …   Wikipedia

  • Calendar era — A calendar era is the year numbering system used by a calendar. For example, the Gregorian calendar numbers its years in the Western Christian era (the Coptic and Ethiopic churches have their own Christian eras, see below). The instant, date, or… …   Wikipedia

  • proleptic — adjective /pɹoʊˈlɛptɪk/ a) Of a calendar, extrapolated to dates prior to its first adoption; of those used to adjust to or from the Julian calendar or Gregorian calendar. b) Describes an event as having been assigned too early a date. Syn:… …   Wiktionary

  • Mesoamerican Long Count calendar — Long Count redirects here. For the 1927 boxing match, see The Long Count Fight. Detail showing three columns of glyphs from a portion of the 2nd century CE La Mojarra Stela 1. The left column gives a Long Count date of 8.5.16.9.7, or 156 CE. The… …   Wikipedia

  • Julian calendar — The Julian calendar began in 45 BC (709 AUC) as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year (known at… …   Wikipedia

  • Revised Julian calendar — The Revised Julian calendar, also known as the Rectified Julian calendar, or, less formally, New calendar, is a calendar, originated in 1923, which effectively discontinued the 340 years of divergence between the naming of dates sanctioned by… …   Wikipedia

  • Maya calendar — Maya civiliza …   Wikipedia

  • Chinese calendar — The Chinese calendar is a lunisolar calendar, incorporating elements of a lunar calendar with those of a solar calendar. It is not exclusive to China, but followed by many other Asian cultures as well.[1] In most of East Asia today, the Gregorian …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”